docstr: Ensure that created columns has `str` type consistently.
docstr_tok: ["Ensure","that","created","columns","has","`","str","`","type","consistently","."]
code: def test_column_name_encoding(self):
      """Ensure that created columns has `str` type consistently."""
      columns = self.spark.createDataFrame(
          [("Alice", 1)], ["name", "age"]
      ).columns
      self.assertEqual(columns, ["name", "age"])
      self.assertTrue(isinstance(columns[0], str))
      self.assertTrue(isinstance(columns[1], str))
  
imports: from itertools import chain
  from pyspark.sql import Column, Row
  from pyspark.sql import functions
  from pyspark.sql.types import StructType, StructField, LongType
  from pyspark.errors import AnalysisException, PySparkTypeError, PySparkValueError
  from pyspark.testing.sqlutils import ReusedSQLTestCase
label_desc: Use image node_id 1 for calling the ColumnTestsMixin obj's underlying member method code with example usage: obj.test_column_name_encoding() without return types