Many to many addition add Method
add(obj1, obj2…)
If the list is used, put the qualified instance Add to the list , Pass in add() function
Then you need to use *args Parameter to deconstruct the list , otherwise add Function does not execute
Such as ：
instance_list = [ obj1, obj2, obj3]
be , Calling add Function ：
This is not going to work ： add(instance_list)
Only in this way can ：add( *instance_list)
