class_docstr: GNNModel 
docstr: get length of etype list 
docstr_tok: ["get","length","of","etype","list"]
code: def get_etype_len(self):
      """get length of etype list"""
      etype2files = helper.parse_files(self.config.etype2files)
      etype_list = util.get_all_edge_type(
          etype2files, self.config.symmetry
      )
      log.info("len of etypes: %s" % len(etype_list))
      return len(etype_list)
  
imports: import os
  import sys
  import math
  import time
  import numpy
  import pickle
  import paddle
  import paddle.fluid.layers
  import paddle.fluid
  import pgl
  from pgl.utils.logger import log
  from .None import layers
  from .None import model_util
  from .None import loss
  import util
  import helper
  from .auto_heter_gnn import AutoHeterGNN
label_desc: Use image node_id 2 for calling the GNNModel obj's underlying member method code with example usage: obj.get_etype_len() and returns: len