input: Write a function to add two matrices. If the matrices are not compatible for addition, return 'Matrices not compatible'. The function should return the result of adding the two matrices.
  def add_matrix(matrix1, matrix2):
      if len(matrix1) != len(matrix2):
          return 'Matrices not compatible'
      if len(matrix1[0]) != len(matrix2[0]):
          return 'Matrices not compatible'
      
      rows = len(matrix1)
      cols = len(matrix1[0])
      result = [[sum(row) for row in zip(*size)] for size in zip(matrix1, matrix2)]
      
      return result
  
  assert add_matrix([[1, 2], [3, 4]], [[2, 3], [4, 5]])==[[3, 5], [7, 9]]
  assert add_matrix([[1, 1], [2, 2]], [[1, 1], [1, 1]])==[[2, 2], [3, 3]]
  assert add_matrix([[5, 6], [7, 8]], [[1, 2], [3, 4]])==[[6, 8], [10, 12]]
  assert add_matrix([[1, 2]], [[3, 4, 5]])=='Matrices not compatible'
  assert add_matrix([], [])=='Matrices not compatible'
output: def add_matrix(matrix1, matrix2):
      if len(matrix1) != len(matrix2) or len(matrix1) == 0 or len(matrix2) == 0:
          return 'Matrices not compatible'
      if len(matrix1[0]) != len(matrix2[0]):
          return 'Matrices not compatible'
      
      result = [[matrix1[i][j] + matrix2[i][j] for j in range(len(matrix1[0]))] for i in range(len(matrix1))]
      
      return result