docs: def add_secedge(self, secedge):
          """
          Parameters
          ----------
          secedge : etree.Element
              etree representation of a <secedge> element
          A <secEdge> element has a cat and a parent attribute,
          but inherits its ID from its parent element.
          It describes a secondary edge in a tree-like syntax representation.
  
          Example
          -------
             <node xml:id="s10_505" cat="VXINF" func="OV" parent="s10_507">
              <secEdge cat="refvc" parent="s10_504"/>
              <word xml:id="s10_6" form="worden" pos="VAPP" lemma="werden%passiv" func="HD" parent="s10_505" dephead="s10_7" deprel="AUX"/>
             </node>
          """
          if self.ignore_secedges is False:
              edge_source = self.get_parent_id(secedge)
              edge_target = self.get_element_id(secedge)
              self.add_edge(edge_source, edge_target,
                            layers={self.ns, self.ns+':secedge'},
                            label='secedge:'+secedge.attrib['cat'],
                            edge_type=dg.EdgeTypes.pointing_relation)