code: def argument(*param_decls, cls=None, **attrs):
      
      return click.argument(*param_decls, cls=cls or Argument, **attrs)
docs: Arguments are positional parameters to a command.  They generally
      provide fewer features than options but can have infinite ``nargs``
      and are required by default.
  
      :param param_decls: the parameter declarations for this option or
                          argument.  This is a list of flags or argument
                          names.
      :param type: the type that should be used.  Either a :class:`ParamType`
                   or a Python type.  The later is converted into the former
                   automatically if supported.
      :param required: controls if this is optional or not.
      :param default: the default value if omitted.  This can also be a callable,
                      in which case it's invoked when the default is needed
                      without any arguments.
      :param callback: a callback that should be executed after the parameter
                       was matched.  This is called as ``fn(ctx, param,
                       value)`` and needs to return the value.  Before Click
                       2.0, the signature was ``(ctx, value)``.
      :param nargs: the number of arguments to match.  If not ``1`` the return
                    value is a tuple instead of single value.  The default for
                    nargs is ``1`` (except if the type is a tuple, then it's
                    the arity of the tuple).
      :param metavar: how the value is represented in the help page.
      :param expose_value: if this is `True` then the value is passed onwards
                           to the command callback and stored on the context,
                           otherwise it's skipped.
      :param is_eager: eager values are processed before non eager ones.  This
                       should not be set for arguments or it will inverse the
                       order of processing.
      :param envvar: a string or list of strings that are environment variables
                     that should be checked.
      :param help: the help string.
      :param hidden: hide this option from help outputs.
                     Default is True, unless help is given.