code: def values_for_column(self, column_name, limit=10000):
          
          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)]
docs: Runs query against sqla to retrieve some
          sample values for the given column.