docs: def get_current_container_id(read_from='/proc/self/cgroup'):
      """
      Get the ID of the container the application is currently running in,
      otherwise return `None` if not running in a container.
  
      This is a best-effort guess, based on cgroups.
  
      :param read_from: the cgroups file to read from (default: `/proc/self/cgroup`)
      """
  
      if not os.path.exists(read_from):
          return
  
      with open(read_from, 'r') as cgroup:
          for line in cgroup:
              if re.match('.*/[0-9a-f]{64}$', line.strip()):
                  return re.sub('.*/([0-9a-f]{64})$', '\\1', line.strip())