class_docstr: A `Callback` that keeps track of the best value in `monitor`.
class_docstr_tok: ["A","`","Callback","`","that","keeps","track","of","the","best","value","in","`","monitor","`","."]
code: def after_fit(self):
      self.run = True
  
imports: from __future__ import annotations
  from ..basics import *
  from .progress import *
  from .fp16 import MixedPrecision
label_desc: Use image node_id 4 for calling the TrackerCallback obj's underlying member method code with example usage: obj.after_fit() without return types