Call a method given some args and kwargs.

        function -- string containing the method name to call
        args -- arguments, either a list or tuple

        returns the result of the method.

        May raise an exception if the method isn't in the dict.

def call(self, function, args=(), kwargs={}):
        """Call a method given some args and kwargs.

        function -- string containing the method name to call
        args -- arguments, either a list or tuple

        returns the result of the method.

        May raise an exception if the method isn't in the dict.

        """
        return self.functions[function](*args, **kwargs)