class_docstr: A ``attr.ib()`` requiring a callable has been set with a value
  that is not callable.
  
  .. versionadded:: 19.2.0
class_docstr_tok: ["A","``","attr.ib","(",")","``","requiring","a","callable","has","been","set","with","a","value","that","is","not","callable",".","..","versionadded",":",":","19.2.0"]
code: def __str__(self):
      return str(self.msg)
  
imports: from __future__ import absolute_import, division, print_function
label_desc: Use image node_id 2 for calling the NotCallableError obj's underlying member method code with example usage: obj.__str__() and returns: str