Runs query against sqla to retrieve some
        sample values for the given column.

def values_for_column(self, column_name, limit=10000):
        """Runs query against sqla to retrieve some
        sample values for the given column.
        """
        cols = {col.column_name: col for col in self.columns}
        target_col = cols[column_name]
        tp = self.get_template_processor()

        qry = (
            select([target_col.get_sqla_col()])
            .select_from(self.get_from_clause(tp))
            .distinct()
        )
        if limit:
            qry = qry.limit(limit)

        if self.fetch_values_predicate:
            tp = self.get_template_processor()
            qry = qry.where(tp.process_template(self.fetch_values_predicate))

        engine = self.database.get_sqla_engine()
        sql = '{}'.format(
            qry.compile(engine, compile_kwargs={'literal_binds': True}),
        )
        sql = self.mutate_query_from_config(sql)

        df = pd.read_sql_query(sql=sql, con=engine)
        return [row[0] for row in df.to_records(index=False)]