code: def vstack(tup):
      
      # Follow numpy.vstack behavior for 1D arrays:
      arrays = list(tup)
      for i in range(len(arrays)):
          if arrays[i].ndim is 1:
              arrays[i] = arrays[i][np.newaxis, :]
      return concatenate(tup, axis=0)
docs: Stack arrays in sequence vertically (row wise), 
      handling ``RemoteArray`` and ``DistArray`` without moving data.
  
      Args:
        tup (sequence of array_like)
  
      Returns: 
        res: `ndarray`, if inputs were all local
             `RemoteArray`, if inputs were all on the same remote engine
             `DistArray`, if inputs were already scattered on different engines