def read(self, parent):
    group = parent.require_group(GROUP_SOURCE)
    position_group = group.require_group(GROUP_POSITIONS)
    self.position_nm.read(position_group)
    direction_group = group.require_group(GROUP_DIRECTION)
    self.direction.read(direction_group)
    self.kinetic_energy_keV = group.attrs[ATTRIBUTE_KINETIC_ENERGY]
    self.mass_amu = group.attrs[ATTRIBUTE_MASS]
    self.atomic_number = group.attrs[ATTRIBUTE_ATOMIC_NUMBER]
def read(self, parent):
    group = parent.require_group(GROUP_SOURCE)
    position_group = group.require_group(GROUP_POSITIONS)
    self.position_nm.read(position_group)
    direction_group = group.require_group(GROUP_DIRECTION)
    self.direction.read(direction_group)
    self.kinetic_energy_keV = group.attrs[ATTRIBUTE_KINETIC_ENERGY]
    self.mass_amu = group.attrs[ATTRIBUTE_MASS]
    self.atomic_number = group.attrs[ATTRIBUTE_ATOMIC_NUMBER]