@property
def n_electrons(self) -> int:
    ' '
    if (self.active_space is None):
        return self.molecule.n_electrons
    else:
        return (2 * len(self.active_space.active_reference_orbitals))
@property
def n_electrons(self) -> int:
    ' '
    if (self.active_space is None):
        return self.molecule.n_electrons
    else:
        return (2 * len(self.active_space.active_reference_orbitals))