code: def log_tensor(tensor):
      return np.log(tensor)
  
imports: from nvidia.dali.pipeline import Pipeline
  import nvidia.dali.ops
  import numpy
  from functools import partial
  from test_utils import compare_pipelines
  from test_utils import RandomDataIterator
  from nose_utils import raises
label_desc: Use image node_id 4 for calling a global function with example usage: log_tensor(tensor) and returns: np