input: Write a function to add two matrices. The function should check if the matrices are compatible for addition (i.e., they must have the same dimensions). If they are compatible, it should return the resultant matrix; otherwise, it should return 'Matrices not compatible'.
  assert add_matrix([[1, 2], [3, 4]], [[5, 6], [7, 8]]) == [[6, 8], [10, 12]]
  assert add_matrix([[1, 2, 3], [4, 5, 6]], [[7, 8, 9], [10, 11, 12]]) == [[8, 10, 12], [14, 16, 18]]
  assert add_matrix([[1, 2], [3, 4]], [[5, 6, 7], [8, 9, 10]]) == 'Matrices not compatible'
  assert add_matrix([[1, 2, 3], [4, 5, 6]], [[7, 8], [9, 10]]) == 'Matrices not compatible'
  assert add_matrix([[1, 2]], [[3, 4]]) == [[4, 6]]
output: def add_matrix(matrix1, matrix2):
      if len(matrix1) != len(matrix2) or any(len(row1) != len(row2) for row1, row2 in zip(matrix1, matrix2)):
          return 'Matrices not compatible'
      return [[matrix1[i][j] + matrix2[i][j] for j in range(len(matrix1[0]))] for i in range(len(matrix1))]