minor docstring fix
minor docstring fix

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