code: def export_flow_di_data(params, plane):
          
          output_flow = eTree.SubElement(plane, BpmnDiagramGraphExport.bpmndi_namespace + consts.Consts.bpmn_edge)
          output_flow.set(consts.Consts.id, params[consts.Consts.id] + "_gui")
          output_flow.set(consts.Consts.bpmn_element, params[consts.Consts.id])
          waypoints = params[consts.Consts.waypoints]
          for waypoint in waypoints:
              waypoint_element = eTree.SubElement(output_flow, "omgdi:waypoint")
              waypoint_element.set(consts.Consts.x, waypoint[0])
              waypoint_element.set(consts.Consts.y, waypoint[1])
docs: Creates a new BPMNEdge XML element for given edge parameters and adds it to 'plane' element.
  
          :param params: dictionary with edge parameters,
          :param plane: object of Element class, representing BPMN XML 'BPMNPlane' element (root for edge DI data).