code: func (h *Handle) SetNetNsIdByPid(pid, nsid int) error {
  	return h.setNetNsId(NETNSA_PID, uint32(pid), uint32(nsid))
  }
docs: // SetNetNSIdByPid sets the ID of the network namespace for a given pid (really thread id).
  // The ID can only be set for namespaces without an ID already set.