code: def put(self, locator = None, component = None):
          
          if component == None:
              raise Exception("Component cannot be null")
  
          self._lock.acquire()
          try:
              self._references.append(Reference(locator, component))
          finally:
              self._lock.release()
docs: Puts a new reference into this reference map.
  
          :param locator: a component reference to be added.
  
          :param component: a locator to find the reference by.