class_docstr: A test PyOperator with no functionality.
class_docstr_tok: ["A","test","PyOperator","with","no","functionality","."]
code: def __call__(self):
      engine_log.info("I'm an NNOperator.")
  
imports: from towhee.operator import PyOperator
  from towhee.utils.log import engine_log
label_desc: Use image node_id 2 for calling the TestPyOperator obj's underlying member method code with example usage: obj.__call__() without return types