code: def container_id(self):
          
          if getattr(self, "_container_id", None):
              return self._container_id
  
          try:
              containers = self.harpoon.docker_api.containers(all=True)
          except ValueError:
              log.warning("Failed to get a list of active docker files")
              containers = []
  
          self._container_id = None
          for container in containers:
              if any(self.name in container.get("Names", []) for name in (self.container_name, "/{0}".format(self.container_name))):
                  self._container_id = container["Id"]
                  break
  
          return self._container_id
docs: Find a container id
  
          If one isn't already set, we ask docker for the container whose name is
          the same as the recorded container_name