class_docstr: Hook executed to save the exponential moving average of the base_model parameters
  and run the meters on this ema_model.
class_docstr_tok: ["Hook","executed","to","save","the","exponential","moving","average","of","the","base_model","parameters","and","run","the","meters","on","this","ema_model","."]
code: def on_phase_start(self, task: "tasks.ClassyTask") -> None:
      # reset the meters at the beginning of the epoch
      for meter in task.ema_meters:
          meter.reset()
  
file_path: vissl/vissl/hooks/ema_hooks.py
imports: import torch
  from classy_vision import tasks
  from classy_vision.generic.distributed_util import is_primary
  from classy_vision.hooks.classy_hook import ClassyHook
  from vissl.hooks.log_hooks import LogLossMetricsCheckpointHook
label_desc: Use image node_id 3 for calling the EmaHook obj's underlying member method code with example usage: obj.on_phase_start(task) without return types