<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def collect(self):
 """Collect the elements in an DataFrame and concatenate the partition."""

        local_df = self._schema_rdd.toPandas()
        correct_idx_df = _update_index_on_df(local_df, self._index_names)
        return correct_idx_df