Adds a command to the command line interface loop.

        Parameters
        ----------
        name : string
            The command.

        method : function(args)
            The function to execute when this command is issued. The argument
            of the function is a list of space separated arguments to the
            command.

        argc : int, optional (default=None)
            The number of expected further arguments. If None arguments are
            not restricted.

        complete : function(args, text), optional (default=None)
            A function that is called to complete further arguments. If None
            no suggestions are made. The function gets the arguments up to the
            incomplete argument (args). text contains the to be completed
            argument. The function must returns a list of suggestions or None
            if text is valid already and there are no further suggestions.

def add_cmd_method(self, name, method, argc=None, complete=None):
        """Adds a command to the command line interface loop.

        Parameters
        ----------
        name : string
            The command.

        method : function(args)
            The function to execute when this command is issued. The argument
            of the function is a list of space separated arguments to the
            command.

        argc : int, optional (default=None)
            The number of expected further arguments. If None arguments are
            not restricted.

        complete : function(args, text), optional (default=None)
            A function that is called to complete further arguments. If None
            no suggestions are made. The function gets the arguments up to the
            incomplete argument (args). text contains the to be completed
            argument. The function must returns a list of suggestions or None
            if text is valid already and there are no further suggestions.
        """
        if ' ' in name:
            raise ValueError("' ' cannot be in command name {0}".format(name))
        self._cmd_methods[name] = method
        self._cmd_argc[name] = argc
        self._cmd_complete[name] = complete