gistfile1.py

class _metadata_property(object):
    
    def __init__(self, key):
        # key name/abstract
        self.key = key
        self.__doc__ = "Accesses %s from metadata dict" %key

    def __get__(self, obj, type=None):
        return obj.metadata[self.key]

    def __set__(self, obj, value):
        obj.metadata[self.key] = value

    def __delete__(self, obj):
        del obj.metadata[self.key]