class_docstr: Base class for all async predictors. 
docstr: Start workers 
docstr_tok: ["Start","workers"]
code: def start(self):
      """Start workers"""
  
imports: from abc import ABCMeta, abstractmethod
  import six
  import tensorflow
  from ..input_source import PlaceholderInput
  from ..tfutils.common import get_tensors_by_names, get_op_tensor_name
  from ..tfutils.tower import PredictTowerContext
label_desc: Use image node_id 2 for calling the AsyncPredictorBase obj's underlying member method code with example usage: obj.start() without return types