code: def tag_ca_geometry(self, force=False, reference_axis=None,
                          reference_axis_name='ref_axis'):
          
          for polymer in self._molecules:
              if polymer.molecule_type == 'protein':
                  polymer.tag_ca_geometry(
                      force=force, reference_axis=reference_axis,
                      reference_axis_name=reference_axis_name)
          return
docs: Tags each `Monomer` in the `Assembly` with its helical geometry.
  
          Parameters
          ----------
          force : bool, optional
              If True the tag will be run even if `Monomers` are already tagged.
          reference_axis : list(numpy.array or tuple or list), optional
              Coordinates to feed to geometry functions that depend on
              having a reference axis.
          reference_axis_name : str, optional
              Used to name the keys in tags at `Chain` and `Residue` level.