input: def transpose(A):
      """
      Optimize the given Python function that processes a 2d array and stores the transpose output in a new array.
      
      >>> transpose([[1, 2, 3], [4, 5, 6]])
      [[1, 4], [2, 5], [3, 6]]
      >>> transpose([[1, 2], [3, 4], [5, 6]])
      [[1, 3, 5], [2, 4, 6]]
      """
      if not A or not A[0]:
          return []
      n = len(A)
      m = len(A[0])
      return [[A[i][j] for i in range(n)] for j in range(m)]
output:     
      if not A or not A[0]:
          return []
      n = len(A)
      m = len(A[0])
      return [[A[i][j] for i in range(n)] for j in range(m)]
  