fixed check_model in ClusterGraph
fixed check_model in ClusterGraph

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