code: def test_identity_serializer_with_custom_content_type():
      identity_serializer = IdentitySerializer(content_type="text/csv")
      assert identity_serializer.serialize(b"a,b\n1,2") == b"a,b\n1,2"
      assert identity_serializer.CONTENT_TYPE == "text/csv"
  
imports: from __future__ import absolute_import
  import io
  import json
  import os
  import numpy
  import pytest
  import scipy.sparse
  from sagemaker.serializers import CSVSerializer, NumpySerializer, JSONSerializer, IdentitySerializer, SparseMatrixSerializer, JSONLinesSerializer, LibSVMSerializer, DataSerializer
  from tests.unit import DATA_DIR
label_desc: Use image node_id 33 for calling a global function with example usage: test_identity_serializer_with_custom_content_type() without return types