docs: def del_variables(self, variables):
          """
          Deletes variables from the NoisyOrModel.
  
          Parameters
          ----------
          variables: list, tuple, dict (array like)
              list of variables to be deleted.
  
          Examples
          --------
          >>> from pgmpy.models import NoisyOrModel
          >>> model = NoisyOrModel(['x1', 'x2', 'x3'], [2, 3, 2], [[0.6, 0.4],
          ...                                                      [0.2, 0.4, 0.7],
          ...                                                      [0.1, 0. 4]])
          >>> model.del_variables(['x1'])
          """
          variables = [variables] if isinstance(variables, six.string_types) else set(variables)
          indices = [index for index, variable in enumerate(self.variables) if variable in variables]
          self.variables = np.delete(self.variables, indices, 0)
          self.cardinality = np.delete(self.cardinality, indices, 0)
          self.inhibitor_probability = [prob_array for index, prob_array in enumerate(self.inhibitor_probability)
                                        if index not in indices]