class_docstr: Raised if an Argument instance is created with invalid or
  inconsistent arguments.
code: def __str__(self):
      if self.option_id:
          return "option %s: %s" % (self.option_id, self.msg)
      else:
          return self.msg
  
imports: import argparse
  import warnings
  import py
  import six
  from _pytest.config.exceptions import UsageError
label_desc: Use image node_id 2 for calling the ArgumentError obj's underlying member method code with example usage: obj.__str__() and returns: unknown, self