'Inplace remove keys from self that are in other.
Examples
>>> s1 = Struct(a=10,b=30)
>>> s2 = Struct(a=40)
>>> s1 -= s2
>>> s1
{\'b\': 30}'

def __isub__(self, other):

    for k in other.keys():
        if (k in self):
            del self[k]
    return self
