Merges the fares if all the attributes are the same.

def _MergeEntities(self, a, b):
    """Merges the fares if all the attributes are the same."""
    scheme = {'price': self._MergeIdentical,
              'currency_type': self._MergeIdentical,
              'payment_method': self._MergeIdentical,
              'transfers': self._MergeIdentical,
              'transfer_duration': self._MergeIdentical}
    return self._SchemedMerge(scheme, a, b)