class_docstr: These test cases exercise the interface to the proto plan
  generation but do not call Spark.
class_docstr_tok: ["These","test","cases","exercise","the","interface","to","the","proto","plan","generation","but","do","not","call","Spark","."]
code: def test_subtract(self):
      # SPARK-41453: test `subtract` API for Python client.
      df1 = self.connect.readTable(table_name=self.tbl_name)
      df2 = self.connect.readTable(table_name=self.tbl_name)
      plan1 = df1.subtract(df2)._plan.to_proto(self.connect)
      self.assertTrue(not plan1.root.set_op.is_all)
      self.assertEqual(
          proto.SetOperation.SET_OP_TYPE_EXCEPT,
          plan1.root.set_op.set_op_type,
      )
  
imports: import unittest
  import uuid
  import datetime
  import decimal
  import math
  from pyspark.testing.connectutils import PlanOnlyTestFixture, should_test_connect, connect_requirement_message
  from pyspark.errors import PySparkValueError
label_desc: Use image node_id 30 for calling the SparkConnectPlanTests obj's underlying member method code with example usage: obj.test_subtract() without return types