<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _maybe_coerce_indexer(self, indexer):
 """ return an indexer coerced to the codes dtype """

        if isinstance(indexer, np.ndarray) and indexer.dtype.kind == 'i':
            indexer = indexer.astype(self._codes.dtype)
        return indexer