improved the _marginalize_single_variable method [refs #137]
improved the _marginalize_single_variable method [refs #137]

sandeepkrjha/pgmpy,jhonatanoliveira/pgmpy,yashu-seth/pgmpy,kislayabhi/pgmpy,anaviltripathi/pgmpy,vivek425ster/pgmpy,pratyakshs/pgmpy,khalibartan/pgmpy,sandeepkrjha/pgmpy,abinashpanda/pgmpy,kris-singh/pgmpy,vivek425ster/pgmpy,ankurankan/pgmpy,ankurankan/pgmpy,kislayabhi/pgmpy,khalibartan/pgmpy,palashahuja/pgmpy,pratyakshs/pgmpy,liquidmetal/pgmpy,liquidmetal/pgmpy,pgmpy/pgmpy,abinashpanda/pgmpy,anaviltripathi/pgmpy,kris-singh/pgmpy,jhonatanoliveira/pgmpy,palashahuja/pgmpy,yashu-seth/pgmpy,pgmpy/pgmpy