<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def filter_data(self, field, filter_value, filter_operator, field_converter=None):
 """Filter the data given the provided. Args: field (string):
 The field to filter on. filter_value (string | list):
 The value to match. filter_operator (string):
 The operator for comparison. field_converter (method):
 A method used to convert the field before comparison. Returns: (set):
 List of matching data objects """

        data = []
        if self._indexes.get(field) is not None:
            data = self._index_filter(
                self._indexes.get(field), filter_value, filter_operator, field_converter
            )
        # else:
        #     data = self._loop_filter(field, filter_value, filter_operator)

        # if set_operator == "intersection":
        #     self._filtered_results.intersection(data)
        # elif set_operator == "union":
        #     self._filtered_results.union(data)
        return set(data)