code: def test_libsvm_serializer_str(libsvm_serializer):
      original = "0 0:1 5:1"
      result = libsvm_serializer.serialize("0 0:1 5:1")
      assert result == original
  
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 41 for calling a global function with example usage: test_libsvm_serializer_str(libsvm_serializer) without return types