code: def __rst2graph(self, rs3_xml_tree):
          
          doc_root = rs3_xml_tree.getroot()
  
          for segment in doc_root.iter('segment'):
              self.__add_segment(segment)
          for group in doc_root.iter('group'):
              self.__add_group(group)
docs: Reads an RST tree (from an ElementTree representation of an RS3
          XML file) and adds all segments (nodes representing text) and
          groups (nonterminal nodes in an RST tree) as well as the
          relationships that hold between them (typed edges) to this
          RSTGraph.
  
          Parameters
          ----------
          rs3_xml_tree : lxml.etree._ElementTree
              lxml ElementTree representation of an RS3 XML file
          tokenize : bool
              If True, the RST segments (i.e. nuclei and satellites) will
              be tokenized and added as additonal token nodes to the
              document graph (with edges from the respective RST segments).
              If False, each RST segment will be labeled with the text it
              represents.