added support for SQLGraph.edges property with __iter__ and __getitem__ methods
added support for SQLGraph.edges property with __iter__ and __getitem__ methods

GenDataPro/pygr,cjlee112/pygr,theoryno3/pygr,cjlee112/pygr,ctb/pygr,ctb/pygr,RitwikGupta/pygr,cjlee112/pygr,ctb/pygr,GenDataPro/pygr,ctb/pygr,theoryno3/pygr,RitwikGupta/pygr,theoryno3/pygr,ctb/pygr,GenDataPro/pygr,RitwikGupta/pygr,cjlee112/pygr