arsing are
    intentionally not finalized.

    Some settings are supported by both options and arguments.

    .. versionchanged:: 2.0
       Changed signature for parameter callback to also be passed the
       parameter.  In Click 2.0, the old callback format will still work,
       but it will raise a warning to give you change to migrate the
       code easier.

    :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.
    Z	parameterNFTc