with data gathered from the C{Options} instance passed in, and its
    base classes.

    @type options: L{twisted.python.usage.Options}
    @ivar options: The L{twisted.python.usage.Options} instance to generate for

    @type cmdName: C{str}
    @ivar cmdName: The name of the command we're generating completions for.

    @type file: C{file}
    @ivar file: The C{file} to write the completion function to.  The C{file}
        must have L{bytes} I/O semantics.

    @type descriptions: C{dict}
    @ivar descriptions: A dict mapping long option names to alternate
        descriptions. When this variable is defined, the descriptions
        contained here will override those descriptions provided in the
        optFlags and optParameters variables.

    @type multiUse: C{list}
    @ivar multiUse: An iterable containing those long option names which may
        appear on the command line more than once. By default, options will
        only be completed one time.

    @type mutuallyExclusive: C{list} of C{tuple}
    @ivar mutuallyExclusive: A sequence of sequences, with each sub-sequence
        containing those long option names that are mutually exclusive. That is,
        those options that cannot appear on the command line together.

    @type optActions: C{dict}
    @ivar optActions: A dict mapping long option names to shell "actions".
        These actions define what may be completed as the argument to the
        given option, and should be given as instances of
        L{twisted.python.usage.Completer}.

        Callables may instead be given for the values in this dict. The
        callable should accept no arguments, and return a C{Completer}
        instance used as the action.

    @type extraActions: C{list} of C{twisted.python.usage.Completer}
    @ivar extraActions: Extra arguments are those arguments typically
        appearing at the end of the command-line, which are not associated
        with any particular named option. That is, the arguments that are
        given to the parseArgs() method of your usage.Options subclass.
    c