code: def test_struct_in_map(self):
      d = [Row(m={Row(i=1): Row(s="")})]
      df = self.spark.createDataFrame(d)
      k, v = list(df.head().m.items())[0]
      self.assertEqual(1, k.i)
      self.assertEqual("", v.s)
  
imports: import datetime
  import shutil
  import tempfile
  import time
  from pyspark.sql import Row
  from pyspark.sql.functions import lit
  from pyspark.sql.types import StructType, StructField, DecimalType, BinaryType
  from pyspark.testing.sqlutils import ReusedSQLTestCase, UTCOffsetTimezone
label_desc: Use image node_id 3 for calling the SerdeTestsMixin obj's underlying member method code with example usage: obj.test_struct_in_map() without return types