Python function to merge 2 dicts, similar to what angular does

Extends

'''
    Extends a dict object A with the properties of a dict object B.
    @param a: dict object
    @param b: dict object
'''
def extends(a, b):
    for key in b:
        if key in a:
            if isinstance(a[key], dict) and isinstance(b[key], dict):
                a[key] = extends(a[key], b[key])
            elif a[key] == b[key]:
                pass # same leaf value
            else:
                a[key] = b[key]
        else:
            a[key] = b[key]
    return a