class_docstr: Base class for decorators to add ArgumentParser information to a method.
      
code: def __call__(self, func):
      if not getattr(func, "has_arguments", False):
          func.has_arguments = True
          func.decorators = []
      func.decorators.append(self)
      return func
  
imports: import argparse
  import re
  from IPython.core.error import UsageError
  from IPython.utils.decorators import undoc
  from IPython.utils.process import arg_split
  from IPython.utils.text import dedent
label_desc: Use image node_id 1 for calling the ArgDecorator obj's underlying member method code with example usage: obj.__call__(func) and returns: func