def _lookup_transformer(self, from_, to_):
    if (from_ == to_):
        return identity_transformer
    try:
        return self._pm.transformers[from_][to_].transformer
    except KeyError:
        return None
def _lookup_transformer(self, from_, to_):
    if (from_ == to_):
        return identity_transformer
    try:
        return self._pm.transformers[from_][to_].transformer
    except KeyError:
        return None