code: def get_text(docgraph, node_id=None):
      
      if node_id:
          tokens = (docgraph.node[node_id][docgraph.ns+':token']
                    for node_id in get_span(docgraph, node_id))
      else:
          tokens = (docgraph.node[token_id][docgraph.ns+':token']
                    for token_id in docgraph.tokens)
      return ' '.join(tokens)
docs: returns the text (joined token strings) that the given node dominates
      or spans. If no node ID is given, returns the complete text of the
      document