code: def test_walk(self):
      const_exp1 = ConstantValueExpression(1)
      const_exp2 = ConstantValueExpression(1)
      const_exp3 = ConstantValueExpression(0)
      const_exp4 = ConstantValueExpression(5)
  
      cmpr_exp1 = ComparisonExpression(
          ExpressionType.COMPARE_GEQ, const_exp1, const_exp2
      )
  
      cmpr_exp2 = ComparisonExpression(
          ExpressionType.COMPARE_GEQ, const_exp3, const_exp4
      )
  
      expr = LogicalExpression(
          ExpressionType.LOGICAL_AND, cmpr_exp1, cmpr_exp2
      )
  
      self.assertEqual(len(list(expr.walk())), 7)
      self.assertEqual(len(list(expr.walk(bfs=False))), 7)
  
      bfs = [
          expr,
          cmpr_exp1,
          cmpr_exp2,
          const_exp1,
          const_exp2,
          const_exp3,
          const_exp4,
      ]
      dfs = [
          expr,
          cmpr_exp1,
          const_exp1,
          const_exp2,
          cmpr_exp2,
          const_exp3,
          const_exp4,
      ]
      self.assertTrue(
          all(
              isinstance(exp, type(bfs[idx]))
              for idx, exp in enumerate(list(expr.walk()))
          )
      )
      self.assertTrue(
          all(
              isinstance(exp, type(dfs[idx]))
              for idx, exp in enumerate(list(expr.walk(bfs=False)))
          )
      )
  
file_path: evadb/test/unit_tests/expression/test_abstract_expression.py
imports: import unittest
  from mock import patch
  from evadb.expression.abstract_expression import AbstractExpression, ExpressionType
  from evadb.expression.comparison_expression import ComparisonExpression
  from evadb.expression.constant_value_expression import ConstantValueExpression
  from evadb.expression.logical_expression import LogicalExpression
  from evadb.expression.tuple_value_expression import TupleValueExpression
label_desc: Use image node_id 1 for calling the AbstractExpressionsTest obj's underlying member method code with example usage: obj.test_walk() without return types