Added dummy __setitem__() and __delitem__() to EnsemblOnDemandSliceDB so that it meets all the requirements of UserDict.DictMixin
Added dummy __setitem__() and __delitem__() to EnsemblOnDemandSliceDB so that it meets all the requirements of UserDict.DictMixin

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