code: def matrix_combine(matrix_1, matrix_2):
      """
      Return the combination of two confusion matrices.
  
      :param matrix_1: first matrix that is going to be combined.
      :type matrix_1: dict
      :param matrix_2: second matrix that is going to be combined.
      :type matrix_2: dict
      :return: the combination of two matrices as a dict of dicts
      """
      result_matrix = {}
      classes_1, classes_2 = matrix_1.keys(), matrix_2.keys()
      classes = set(classes_1).union(set(classes_2))
      for class_1 in classes:
          temp_dict = {}
          for class_2 in classes:
              tmp = 0
              if class_1 in classes_1 and class_2 in classes_1:
                  tmp += matrix_1[class_1][class_2]
              if class_1 in classes_2 and class_2 in classes_2:
                  tmp += matrix_2[class_1][class_2]
              temp_dict[class_2] = tmp
          result_matrix[class_1] = temp_dict
      return result_matrix
  
imports: from __future__ import division
  import sys
  import math
  import numpy
  import re
  from .pycm_param import *
  from .pycm_error import pycmMatrixError
  from warnings import warn
  from functools import wraps
label_desc: Use image node_id 22 for calling a global function with example usage: matrix_combine(matrix_1, matrix_2) and returns: result_matrix