<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def tag_torsion_angles(self, force=False):
 """Tags each `Monomer` in the `Assembly` with its torsion angles. Parameters force : bool, optional If `True`, the tag will be run even if `Monomers` are already tagged. """

        for polymer in self._molecules:
            if polymer.molecule_type == 'protein':
                polymer.tag_torsion_angles(force=force)
        return