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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _index_command(self, type, columns, index):
 """ Add a new index command to the blueprint. :param type: The index type :type type: str :param columns: The index columns :type columns: list or str :param index: The index name :type index: str :rtype: Fluent """

        if not isinstance(columns, list):
            columns = [columns]

        if not index:
            index = self._create_index_name(type, columns)

        return self._add_command(type, index=index, columns=columns)