class_docstr: Build learning rate variable
  https://www.paddlepaddle.org.cn/documentation/docs/zh/api_cn/layers_cn.html
  Args:
      function(str): class name of learning rate
      params(dict): parameters used for init the class
class_docstr_tok: ["Build","learning","rate","variable","https",":","\/\/www.paddlepaddle.org.cn\/documentation\/docs\/zh\/api_cn\/layers_cn.html","Args",":","function","(","str",")",":","class","name","of","learning","rate","params","(","dict",")",":","parameters","used","for","init","the","class"]
code: def __call__(self):
      mod = sys.modules[__name__]
      lr = getattr(mod, self.function)(**self.params)
      return lr
  
imports: import sys
  import math
  from paddle.optimizer.lr import LinearWarmup
  from paddle.optimizer.lr import PiecewiseDecay
  from paddle.optimizer.lr import CosineAnnealingDecay
  from paddle.optimizer.lr import ExponentialDecay
  import paddle
  import paddle.regularizer
  from copy import deepcopy
label_desc: Use image node_id 2 for calling the LearningRateBuilder obj's underlying member method code with example usage: obj.__call__() and returns: lr