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_drop_na(self):
      # SPARK-41148: Test drop na
      df = self.connect.readTable(table_name=self.tbl_name)
  
      plan = df.dropna()._plan.to_proto(self.connect)
      self.assertEqual(plan.root.drop_na.cols, [])
      self.assertEqual(
          plan.root.drop_na.HasField("min_non_nulls"), False
      )
  
      plan = df.na.drop(
          thresh=2, subset=("col_a", "col_b")
      )._plan.to_proto(self.connect)
      self.assertEqual(plan.root.drop_na.cols, ["col_a", "col_b"])
      self.assertEqual(plan.root.drop_na.min_non_nulls, 2)
  
      plan = df.dropna(how="all", subset="col_c")._plan.to_proto(
          self.connect
      )
      self.assertEqual(plan.root.drop_na.cols, ["col_c"])
      self.assertEqual(plan.root.drop_na.min_non_nulls, 1)
  
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 9 for calling the SparkConnectPlanTests obj's underlying member method code with example usage: obj.test_drop_na() without return types