code: def test_nested_array_input(self):
      df = self.spark.range(1).selectExpr(
          "array(array(1, 2), array(3, 4)) as nested_array"
      )
      self.assertEqual(
          df.select(
              udf(lambda x: str(x), returnType="string", useArrow=True)(
                  "nested_array"
              )
          ).first()[0],
          "[[1, 2], [3, 4]]",
      )
  
imports: import unittest
  from pyspark.errors import PythonException, PySparkNotImplementedError
  from pyspark.sql import Row
  from pyspark.sql.functions import udf
  from pyspark.sql.tests.test_udf import BaseUDFTestsMixin
  from pyspark.sql.types import VarcharType
  from pyspark.testing.sqlutils import have_pandas, have_pyarrow, pandas_requirement_message, pyarrow_requirement_message, ReusedSQLTestCase
  from pyspark.rdd import PythonEvalType
label_desc: Use image node_id 8 for calling the PythonUDFArrowTestsMixin obj's underlying member method code with example usage: obj.test_nested_array_input() without return types