fixes issue with factor reduce when the nodes are tuples
fixes issue with factor reduce when the nodes are tuples

ankurankan/pgmpy,jhonatanoliveira/pgmpy,yashu-seth/pgmpy,anaviltripathi/pgmpy,yashu-seth/pgmpy,kris-singh/pgmpy,sandeepkrjha/pgmpy,khalibartan/pgmpy,liquidmetal/pgmpy,liquidmetal/pgmpy,kris-singh/pgmpy,sandeepkrjha/pgmpy,palashahuja/pgmpy,pgmpy/pgmpy,pgmpy/pgmpy,anaviltripathi/pgmpy,palashahuja/pgmpy,ankurankan/pgmpy,abinashpanda/pgmpy,khalibartan/pgmpy,abinashpanda/pgmpy,jhonatanoliveira/pgmpy