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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 _show_tables(self, *args):
 """ print the existing tables within the 'doc' schema """

        v = self.connection.lowest_server_version
        schema_name = \
            "table_schema" if v >= TABLE_SCHEMA_MIN_VERSION else "schema_name"
        table_filter = \
            " AND table_type = 'BASE TABLE'" if v >= TABLE_TYPE_MIN_VERSION else ""

        self._exec("SELECT format('%s.%s', {schema}, table_name) AS name "
                   "FROM information_schema.tables "
                   "WHERE {schema} NOT IN ('sys','information_schema', 'pg_catalog')"
                   "{table_filter}"
                   .format(schema=schema_name, table_filter=table_filter))