input: Write a function to take a 2D array as input and return its transpose stored in a new array.
  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
  assert transpose([[1, 2, 3], [4, 5, 6]])==[[1, 4], [2, 5], [3, 6]]
  assert transpose([[7, 8], [9, 10], [11, 12]])==[[7, 9, 11], [8, 10, 12]]
  assert transpose([[]])==[[]]
  assert transpose([[1]])==[[1]]
  assert transpose([[1, 2], [3, 4]])==[[1, 3], [2, 4]]
output: 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