class_docstr: Indicator for periodically resetting the tree state after a certain time.
  
  The indicator will maintain a state to track the previous restart time.
class_docstr_tok: ["Indicator","for","periodically","resetting","the","tree","state","after","a","certain","time",".","The","indicator","will","maintain","a","state","to","track","the","previous","restart","time","."]
docstr: Returns initial time as state.
docstr_tok: ["Returns","initial","time","as","state","."]
code: def initialize(self):
      """Returns initial time as state."""
      return tf.timestamp()
  
imports: import abc
  import collections
  from typing import Optional
  import tensorflow
  from tensorflow_privacy.privacy.dp_query import dp_query
label_desc: Use image node_id 2 for calling the PeriodicTimeRestartIndicator obj's underlying member method code with example usage: obj.initialize() and returns: tf