code: def _external2internal_func(bounds):
      
      ls = [_external2internal_lambda(b) for b in bounds]
  
      def convert_e2i(xe):
          xi = empty_like(xe)
          xi[:] = [l(p) for l, p in zip(ls, xe)]
          return xi
  
      return convert_e2i
docs: Make a function which converts between external (constrained) and
      internal (unconstrained) parameters.