code: def indexableText(self, include_properties=True):
          
          text = set()
          for extractor in self._text_extractors:
              if extractor.content_type in self.content_types.overrides:
                  for tree in self.content_types.getTreesFor(self, extractor.content_type):
                      words = extractor.indexableText(tree)
                      text |= words
  
          if include_properties:
              for prop_value in self.allProperties.values():
                  if prop_value is not None:
                      text.add(prop_value)
          return u' '.join([word for word in text])
docs: Words found in the various texts of the document.
  
          :param include_properties: Adds words from properties
          :return: Space separated words of the document.