code: func (h *Hash) Set(key, val Value) error {
  	keyVal := key.MrbValue(&Mrb{h.state}).value
  	valVal := val.MrbValue(&Mrb{h.state}).value
  	C.mrb_hash_set(h.state, h.value, keyVal, valVal)
  	return nil
  }
docs: // Set sets a value on the hash