uple of positional arguments, and a dict of
    keyword arguments, and return a mapping of arguments that were actually
    passed to their passed values.

    @param argspec: The argument specification for the function to inspect.
    @type argspec: I{inspect.ArgSpec}

    @param positional: The positional arguments that were passed.
    @type positional: L{tuple}

    @param keyword: The keyword arguments that were passed.
    @type keyword: L{dict}

    @return: A dictionary mapping argument names (those declared in C{argspec})
        to values that were passed explicitly by the user.
    @rtype: L{dict} mapping L{str} to L{object}
    Nr