id() is a built-in function in Python, so rename the property to link_id. Add
a scope_path StringProperty to cache the string representation of the
transitive closure of the nested scopes of an entity.
Patch by: Todd Larsen
"""Multi-consumer multi-producer dispatching mechanism
Originally based on pydispatch (BSD) http://pypi.python.org/pypi/PyDispatcher/2.0.1
See license.txt for original license.
Heavily modified for Django's purposes.
"""
from django.dispatch.dispatcher import Signal