code: def ungrounded_texts(stmts):
      
      ungrounded = [ag.db_refs['TEXT']
                    for s in stmts
                    for ag in s.agent_list()
                    if ag is not None and list(ag.db_refs.keys()) == ['TEXT']]
      ungroundc = Counter(ungrounded)
      ungroundc = ungroundc.items()
      ungroundc = sorted(ungroundc, key=lambda x: x[1], reverse=True)
      return ungroundc
docs: Return a list of all ungrounded entities ordered by number of mentions
  
      Parameters
      ----------
      stmts : list of :py:class:`indra.statements.Statement`
  
      Returns
      -------
      ungroundc : list of tuple
         list of tuples of the form (text: str, count: int) sorted in descending
         order by count.