input: 
  def transpose(A):
      n = len(A)
      m = len(A[0])
  
      B = [[0 for x in range(n)] for x in range(m)]
  
      for i in range(n):
          for j in range(m):
              B[j][i] = A[i][j]
  
      return B
  
  # Example:
  # for transpose([[1, 2, 3], [4, 5, 6]]) == [[1, 4], [2, 5], [3, 6]]
  
output:     for i in range(n):
          for j in range(m):
              B[j][i] = A[i][j]
  
      return B