def __init__(self, parentBucket=None):
        """
        Create a L{Bucket} that may have a parent L{Bucket}.

        @param parentBucket: If a parent Bucket is specified,
            all L{add} and L{drip} operations on this L{Bucket}
            will be applied on the parent L{Bucket} as well.
        @type parentBucket: L{Bucket}
        """
        self.content = 0
        self.parentBucket = parentBucket
        self.lastDrip = time()

        Create a L{Bucket} that may have a parent L{Bucket}.

        @param parentBucket: If a parent Bucket is specified,
            all L{add} and L{drip} operations on this L{Bucket}
            will be applied on the parent L{Bucket} as well.
        @type parentBucket: L{Bucket}
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/protocols/htb.py