class_docstr: Sort the frames which satisfy the condition
  
  Arguments:
      node (AbstractPlan): The OrderBy Plan
docstr: extracts the string name of the column
docstr_tok: ["extracts","the","string","name","of","the","column"]
code: def extract_column_names(self):
      """extracts the string name of the column"""
      # self._columns: List[TupleValueExpression]
      col_name_list = []
      for col in self._columns:
          col_name_list += self._extract_column_name(col)
      return col_name_list
  
file_path: evadb/evadb/executor/orderby_executor.py
imports: from typing import Iterator
  from evadb.database import EvaDBDatabase
  from evadb.executor.abstract_executor import AbstractExecutor
  from evadb.executor.executor_utils import ExecutorError
  from evadb.expression.function_expression import FunctionExpression
  from evadb.expression.tuple_value_expression import TupleValueExpression
  from evadb.models.storage.batch import Batch
  from evadb.parser.types import ParserOrderBySortType
  from evadb.plan_nodes.orderby_plan import OrderByPlan
label_desc: Use image node_id 3 for calling the OrderByExecutor obj's underlying member method code with example usage: obj.extract_column_names() and returns: col_name_list