class_docstr: Implemetation of skipgram model.
  
  Args:
      config: dict, some configure parameters.
      dataset: instance of Dataset class
      place: GPU or CPU place
class_docstr_tok: ["Implemetation","of","skipgram","model",".","Args",":","config",":","dict",",","some","configure","parameters",".","dataset",":","instance","of","Dataset","class","place",":","GPU","or","CPU","place"]
docstr: Build the optimizer.
          
docstr_tok: ["Build","the","optimizer","."]
code: def backward(self, global_steps, opt_config):
      """Build the optimizer."""
      self.lr = fl.polynomial_decay(
          opt_config["lr"], global_steps, opt_config["end_lr"]
      )
      adam = fluid.optimizer.Adam(learning_rate=self.lr)
      adam.minimize(self.loss)
  
file_path: PGL/legacy/examples/metapath2vec/model.py
imports: import argparse
  import time
  import math
  import os
  import io
  from multiprocessing import Pool
  import logging
  import numpy
  import glob
  import pgl
  from pgl import data_loader
  from pgl.utils import op
  from pgl.utils.logger import log
  import paddle.fluid
  import paddle.fluid.layers
label_desc: Use image node_id 2 for calling the SkipgramModel obj's underlying member method code with example usage: obj.backward(global_steps, opt_config) without return types