input: def add_matrix(matrix1, matrix2):
      """
      Adds two matrices together. If the matrices are not compatible (different 
      dimensions), it returns 'Matrices not compatible'.
  
      >>> add_matrix([[1, 2], [3, 4]], [[5, 6], [7, 8]])
      [[6, 8], [10, 12]]
      >>> add_matrix([[1, 2], [3, 4]], [[1, 2, 3], [4, 5, 6]])
      'Matrices not compatible'
      """
      if len(matrix1) != len(matrix2) or len(matrix1[0]) != len(matrix2[0]):
          return 'Matrices not compatible'
      
      return [[matrix1[i][j] + matrix2[i][j] for j in range(len(matrix1[0]))] for i in range(len(matrix1))]
output:     if len(matrix1) != len(matrix2) or len(matrix1[0]) != len(matrix2[0]):
          return 'Matrices not compatible'
      
      return [[matrix1[i][j] + matrix2[i][j] for j in range(len(matrix1[0]))] for i in range(len(matrix1))]