Remove unused subfields from AuxSubfieldsPoroelasticity
## Description

`AuxSubfieldsPoroelasticity.py` contains lots of subfields that do not seem to be used in the Poroelasticity formulation. The Python object has shear modulus, solid bulk modulus, fluid bulk modulus, undrained bulk modulus, drained bulk modulus, Young's modulus, and Poisson's ratio. It looks like most of these are not used in the C++ object.

## Desired Solution

Remove unused subfields from `AuxSubfieldsPoroelasticity.py`.

@rwalkerlewis Please submit a PR to resolve this issue ASAP.
diff --git a/libsrc/pylith/materials/AuxiliaryFactoryPoroelastic.cc b/libsrc/pylith/materials/AuxiliaryFactoryPoroelastic.cc
index c5ca5e522..10bb5d446 100644
--- a/libsrc/pylith/materials/AuxiliaryFactoryPoroelastic.cc
+++ b/libsrc/pylith/materials/AuxiliaryFactoryPoroelastic.cc
@@ -138,61 +138,6 @@ pylith::materials::AuxiliaryFactoryPoroelastic::addDrainedBulkModulus(void) { //
     PYLITH_METHOD_END;
 } // addDrainedBulkModulus
 
-
-// --------------------------------------------------------------------
-// Add undrained bulk modulus subfield to auxiliary fields.
-void
-pylith::materials::AuxiliaryFactoryPoroelastic::addUndrainedBulkModulus(void) { // UndrainedBulkModulus
-    PYLITH_METHOD_BEGIN;
-    PYLITH_JOURNAL_DEBUG("addUndrainedBulkModulus(void)");
-
-    const char* subfieldName = "undrained_bulk_modulus";
-    const PylithReal pressureScale = _normalizer->getPressureScale();
-
-    pylith::topology::Field::Description description;
-    description.label = subfieldName;
-    description.alias = subfieldName;
-    description.vectorFieldType = pylith::topology::Field::SCALAR;
-    description.numComponents = 1;
-    description.componentNames.resize(1);
-    description.componentNames[0] = subfieldName;
-    description.scale = pressureScale;
-    description.validator = pylith::topology::FieldQuery::validatorPositive;
-
-    _field->subfieldAdd(description, getSubfieldDiscretization(subfieldName));
-    this->setSubfieldQuery(subfieldName);
-
-    PYLITH_METHOD_END;
-} // addUndrainedBulkModulus
-
-
-// --------------------------------------------------------------------
-// Add fluid bulk modulus subfield to auxiliary fields.
-void
-pylith::materials::AuxiliaryFactoryPoroelastic::addFluidBulkModulus(void) { // fluidBulkModulus
-    PYLITH_METHOD_BEGIN;
-    PYLITH_JOURNAL_DEBUG("addFluidBulkModulus(void)");
-
-    const char* subfieldName = "fluid_bulk_modulus";
-    const PylithReal pressureScale = _normalizer->getPressureScale();
-
-    pylith::topology::Field::Description description;
-    description.label = subfieldName;
-    description.alias = subfieldName;
-    description.vectorFieldType = pylith::topology::Field::SCALAR;
-    description.numComponents = 1;
-    description.componentNames.resize(1);
-    description.componentNames[0] = subfieldName;
-    description.scale = pressureScale;
-    description.validator = pylith::topology::FieldQuery::validatorPositive;
-
-    _field->subfieldAdd(description, getSubfieldDiscretization(subfieldName));
-    this->setSubfieldQuery(subfieldName);
-
-    PYLITH_METHOD_END;
-} // addFluidBulkModulus
-
-
 // ---------------------------------------------------------------------
 // Add biot coefficient subfield to auxiliary fields.
 void
@@ -350,86 +295,4 @@ pylith::materials::AuxiliaryFactoryPoroelastic::addShearModulus(void) {
 } // addShearModulus
 
 
-// ---------------------------------------------------------------------------------------------------------------------
-// Add solid bulk modulus subfield to auxiliary fields.
-void
-pylith::materials::AuxiliaryFactoryPoroelastic::addSolidBulkModulus(void) {
-    PYLITH_METHOD_BEGIN;
-    PYLITH_JOURNAL_DEBUG("addSolidBulkModulus(void)");
-
-    const char* subfieldName = "solid_bulk_modulus";
-    const PylithReal pressureScale = _normalizer->getPressureScale();
-
-    pylith::topology::Field::Description description;
-    description.label = subfieldName;
-    description.alias = subfieldName;
-    description.vectorFieldType = pylith::topology::Field::SCALAR;
-    description.numComponents = 1;
-    description.componentNames.resize(1);
-    description.componentNames[0] = subfieldName;
-    description.scale = pressureScale;
-    description.validator = pylith::topology::FieldQuery::validatorPositive;
-
-    _field->subfieldAdd(description, getSubfieldDiscretization(subfieldName));
-    this->setSubfieldQuery(subfieldName);
-
-    PYLITH_METHOD_END;
-} // addSolidBulkModulus
-
-
-// ---------------------------------------------------------------------------------------------------------------------
-// Add young's modulus subfield to auxiliary fields.
-void
-pylith::materials::AuxiliaryFactoryPoroelastic::addYoungsModulus(void) {
-    PYLITH_METHOD_BEGIN;
-    PYLITH_JOURNAL_DEBUG("addYoungsModulus(void)");
-
-    const char* subfieldName = "youngs_modulus";
-    const PylithReal pressureScale = _normalizer->getPressureScale();
-
-    pylith::topology::Field::Description description;
-    description.label = subfieldName;
-    description.alias = subfieldName;
-    description.vectorFieldType = pylith::topology::Field::SCALAR;
-    description.numComponents = 1;
-    description.componentNames.resize(1);
-    description.componentNames[0] = subfieldName;
-    description.scale = pressureScale;
-    description.validator = pylith::topology::FieldQuery::validatorPositive;
-
-    _field->subfieldAdd(description, getSubfieldDiscretization(subfieldName));
-    this->setSubfieldQuery(subfieldName);
-
-    PYLITH_METHOD_END;
-} // addYoungsModulus
-
-
-// ----------------------------------------------------------------------
-// Add poisson's ratio subfield to auxiliary fields.
-void
-pylith::materials::AuxiliaryFactoryPoroelastic::addPoissonsRatio(void) { // porosity
-    PYLITH_METHOD_BEGIN;
-    PYLITH_JOURNAL_DEBUG("addPoissonsRatio(void)");
-
-    const char* subfieldName = "poissons_ratio";
-
-    const PylithReal noScale = 1;
-
-    pylith::topology::Field::Description description;
-    description.label = subfieldName;
-    description.alias = subfieldName;
-    description.vectorFieldType = pylith::topology::Field::SCALAR;
-    description.numComponents = 1;
-    description.componentNames.resize(1);
-    description.componentNames[0] = subfieldName;
-    description.scale = noScale;
-    description.validator = pylith::topology::FieldQuery::validatorNonnegative;
-
-    _field->subfieldAdd(description, getSubfieldDiscretization(subfieldName));
-    this->setSubfieldQuery(subfieldName);
-
-    PYLITH_METHOD_END;
-} // addPoissonsRatio
-
-
 // End of file
diff --git a/libsrc/pylith/materials/AuxiliaryFactoryPoroelastic.hh b/libsrc/pylith/materials/AuxiliaryFactoryPoroelastic.hh
index 282ec10e6..0bfbbf31c 100644
--- a/libsrc/pylith/materials/AuxiliaryFactoryPoroelastic.hh
+++ b/libsrc/pylith/materials/AuxiliaryFactoryPoroelastic.hh
@@ -48,12 +48,6 @@ public:
     /// Add drained Bulk Modulus subfield to auxiliary subfields.
     void addDrainedBulkModulus(void);
 
-    /// Add undrained Bulk Modulus subfield to auxiliary subfields.
-    void addUndrainedBulkModulus(void);
-
-    /// Add fluid Bulk Modulus subfield to auxiliary subfields.
-    void addFluidBulkModulus(void);
-
     /// Add fluid Biot Coefficient subfield to auxiliary subfields.
     void addBiotCoefficient(void);
 
@@ -69,15 +63,6 @@ public:
     /// Add shear modulus subfield to auxiliary subfields.
     void addShearModulus(void);
 
-    /// Add solid bulk modulus subfield to auxiliary subfields.
-    void addSolidBulkModulus(void);
-
-    /// Add shear modulus subfield to auxiliary subfields.
-    void addYoungsModulus(void);
-
-    /// Add solid bulk modulus subfield to auxiliary subfields.
-    void addPoissonsRatio(void);
-
     // NOT IMPLEMENTED /////////////////////////////////////////////////////////////////////////////////////////////////
 private:
 
diff --git a/pylith/materials/AuxSubfieldsIsotropicLinearPoroelasticity.py b/pylith/materials/AuxSubfieldsIsotropicLinearPoroelasticity.py
index f0af43787..1a45d71fb 100644
--- a/pylith/materials/AuxSubfieldsIsotropicLinearPoroelasticity.py
+++ b/pylith/materials/AuxSubfieldsIsotropicLinearPoroelasticity.py
@@ -58,34 +58,14 @@ class AuxSubfieldsIsotropicLinearPoroelasticity(PetscComponent):
         "tensor_permeability", family="auxiliary_subfield", factory=Subfield)
     tensorPermeability.meta['tip'] = "Tensor permeability subfield."
 
-    solidBulkModulus = pythia.pyre.inventory.facility(
-        "solid_bulk_modulus", family="auxiliary_subfield", factory=Subfield)
-    solidBulkModulus.meta['tip'] = "Solid bulk modulus subfield."
-
-    fluidBulkModulus = pythia.pyre.inventory.facility(
-        "fluid_bulk_modulus", family="auxiliary_subfield", factory=Subfield)
-    fluidBulkModulus.meta['tip'] = "Fluid bulk modulus subfield."
-
     drainedBulkModulus = pythia.pyre.inventory.facility(
         "drained_bulk_modulus", family="auxiliary_subfield", factory=Subfield)
     drainedBulkModulus.meta['tip'] = "Drained bulk modulus subfield."
 
-    undrainedBulkModulus = pythia.pyre.inventory.facility(
-        "undrained_bulk_modulus", family="auxiliary_subfield", factory=Subfield)
-    undrainedBulkModulus.meta['tip'] = "Undrained bulk modulus subfield."
-
     biotModulus = pythia.pyre.inventory.facility(
         "biot_modulus", family="auxiliary_subfield", factory=Subfield)
     biotModulus.meta['tip'] = "Biot modulus subfield."
 
-    youngsModulus = pythia.pyre.inventory.facility(
-        "youngs_modulus", family="auxiliary_subfield", factory=Subfield)
-    youngsModulus.meta['tip'] = "Young's modulus subfield."
-
-    poissonsRatio = pythia.pyre.inventory.facility(
-        "poissons_ratio", family="auxiliary_subfield", factory=Subfield)
-    poissonsRatio.meta['tip'] = "Poisson's ratio subfield."
-
     # PUBLIC METHODS /////////////////////////////////////////////////////
 
     def __init__(self, name="auxfieldsisotropiclinearporoelasticity"):
['libsrc/pylith/materials/AuxiliaryFactoryPoroelastic.cc', 'pylith/materials/AuxSubfieldsIsotropicLinearPoroelasticity.py', 'libsrc/pylith/materials/AuxiliaryFactoryPoroelastic.hh']