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])

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)