def get_tx_mapping_options(self, tx_ac):
rows = self._fetchall(self._queries['<STR_LIT>'], [tx_ac])<EOL>return rows<EOL>
Return all transcript alignment sets for a given transcript
        accession (tx_ac); returns empty list if transcript does not
        exist.  Use this method to discovery possible mapping options
        supported in the database

        :param tx_ac: transcript accession with version (e.g., 'NM_000051.3')
        :type tx_ac: str

        # database output
        -[ RECORD 1 ]--+------------
        hgnc           | ATM
        cds_start_i    | 385
        cds_end_i      | 9556
        tx_ac          | NM_000051.3
        alt_ac         | AC_000143.1
        alt_aln_method | splign
        -[ RECORD 2 ]--+------------
        hgnc           | ATM
        cds_start_i    | 385
        cds_end_i      | 9556
        tx_ac          | NM_000051.3
        alt_ac         | NC_000011.9
        alt_aln_method | blat