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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def parameter_struct_dict(self):
 """Dictionary containing PyAtomData structs for the force field."""

        if self._parameter_struct_dict is None:
            self._parameter_struct_dict = self._make_ff_params_dict()
        elif self.auto_update_f_params:
            new_hash = hash(
                tuple([tuple(item)
                       for sublist in self.values()
                       for item in sublist.values()]))
            if self._old_hash != new_hash:
                self._parameter_struct_dict = self._make_ff_params_dict()
                self._old_hash = new_hash
        return self._parameter_struct_dict