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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def marginalize(self, variables, inplace=True):
 """ Modifies the factor with marginalized values. Parameters variables: list, array-like List of variables over which to marginalize. inplace: boolean If inplace=True it will modify the factor itself, else would return a new factor. Returns ------- DiscreteFactor or None: if inplace=True (default) returns None if inplace=False returns a new `DiscreteFactor` instance. Examples -------- array([ 14., 22., 30.]) ['x2'] """


        if isinstance(variables, six.string_types):
            raise TypeError("variables: Expected type list or array-like, got type str")

        phi = self if inplace else self.copy()

        for var in variables:
            if var not in phi.variables:
                raise ValueError("{var} not in scope.".format(var=var))

        var_indexes = [phi.variables.index(var) for var in variables]

        index_to_keep = sorted(set(range(len(self.variables))) - set(var_indexes))
        phi.variables = [phi.variables[index] for index in index_to_keep]
        phi.cardinality = phi.cardinality[index_to_keep]

        phi.values = np.sum(phi.values, axis=tuple(var_indexes))

        if not inplace:
            return phi