added import statement in all the examples
added import statement in all the examples

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