remove html arg from _str method because not being used anywhere right now
remove html arg from _str method because not being used anywhere right now

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