docs: def setDocuments(self, documenting_pid, documented_pid):
          """Add a CiTO, the Citation Typing Ontology, triple asserting that
          ``documenting_pid`` documents ``documented_pid``.
  
          Adds assertion: ``documenting_pid cito:documents documented_pid``
  
          Args:
            documenting_pid: str
              PID of a Science Object that documents ``documented_pid``.
  
            documented_pid: str
              PID of a Science Object that is documented by ``documenting_pid``.
  
          """
          self._check_initialized()
          documenting_id = self.getObjectByPid(documenting_pid)
          documented_id = self.getObjectByPid(documented_pid)
          self.add((documenting_id, CITO.documents, documented_id))