code: def hstack(tup):
      
      vals, bounds = zip(*tup)
      stackvalue = np.hstack(vals)
      stackbounds = list(chain(*bounds))
  
      return stackvalue, stackbounds
docs: Horizontally stack a sequence of value bounds pairs.
  
      Parameters
      ----------
      tup: sequence
          a sequence of value, ``Bound`` pairs
  
      Returns
      -------
      value: ndarray
          a horizontally concatenated array1d
      bounds:
          a list of Bounds