docs: def add_variables_from(self, variables, cards):
          """
          Add several variables to the model at once.
  
          Parameters:
          -----------
          variables: array-like iterable object
              List of variables to be added.
  
          cards: array-like iterable object
              List of cardinalities of the variables to be added.
  
          Examples:
          ---------
          >>> from pgmpy.models import MarkovChain as MC
          >>> model = MC()
          >>> model.add_variables_from(['x', 'y'], [3, 4])
          """
          for var, card in zip(variables, cards):
              self.add_variable(var, card)