'Registers another :class:`Command` with this group.  If the name
is not provided, the name of the command is used.'

def add_command(self, cmd, name=None):

    name = (name or cmd.name)
    if (name is None):
        raise TypeError('Command    has    no    name.')
    _check_multicommand(self, name, cmd, register=True)
    self.commands[name] = cmd
