code: def _call_func(func, xs):
      outs = func(*xs)
  
      if isinstance(outs, tuple):
          for i, out in enumerate(outs):
              if isinstance(out, variable.Variable):
                  continue
              n = i + 1
              suffix = {1: "st", 2: "nd", 3: "rd"}.get(
                  n if n < 20 else n % 10, "th"
              )
              msg = (
                  "{}{} element of a returned tuple is not Variable, "
                  "but is {}"
              ).format(n, suffix, type(out))
              raise RuntimeError(msg)
      elif isinstance(outs, variable.Variable):
          outs = (outs,)
      else:
          msg = (
              "A tuple of Variables or a Variable are expected, but {} "
              "is returned.".format(type(outs))
          )
          raise RuntimeError(msg)
  
      return outs
  
file_path: chainer/chainer/functions/util/forget.py
imports: import chainer
  from chainer import function
  from chainer import function_node
  from chainer import variable
label_desc: Use image node_id 1 for calling a global function with example usage: _call_func(func, xs) and returns: outs