code: def get_staged_signatures(vcs):
      
      staged_path = _get_staged_history_path(vcs)
      known_signatures = []
      if os.path.exists(staged_path):
          with open(staged_path, 'r') as f:
              known_signatures = f.read().split()
      return known_signatures
docs: Get the list of staged signatures
  
      Args:
          vcs (easyci.vcs.base.Vcs)
  
      Returns:
          list(basestring) - list of signatures