code: def get_metric(revision, operator, path, key):
      
      if ":" in path:
          part, entry = path.split(":")
          val = revision[operator][part][entry][key]
      else:
          val = revision[operator][path][key]
      return val
docs: Get a metric from the cache.
  
      :param revision: The revision id.
      :type  revision: ``str``
  
      :param operator: The operator name.
      :type  operator: ``str``
  
      :param path: The path to the file/function
      :type  path: ``str``
  
      :param key: The key of the data
      :type  key: ``str``
  
      :return: Data from the cache
      :rtype: ``dict``