def pop(self, key, *args):
        try:
            return self.maps[0].pop(key, *args)
        except KeyError:
            raise KeyError('Key not found in the first mapping: {!r}'.format(key))
Remove *key* from maps[0] and return its value. Raise KeyError if *key* not in maps[0].
dataset/ETHPy150Open ionelmc/python-aspectlib/src/aspectlib/py2chainmap.py/ChainMap.pop