def popitem(self):
        try:
            return self.maps[0].popitem()
        except KeyError:
            raise KeyError('No keys found in the first mapping.')
Remove and return an item pair from maps[0]. Raise KeyError is maps[0] is empty.
dataset/ETHPy150Open ionelmc/python-aspectlib/src/aspectlib/py2chainmap.py/ChainMap.popitem