code: def _write_indicator(self, global_step: int, indicator: Indicator):
      if indicator.is_empty():
          return
  
      if isinstance(indicator, NumericIndicator):
          value = indicator.get_mean()
          key = self._parse_key(indicator.mean_key)
          if key not in self.indicators:
              self.indicators[key] = []
  
          self.indicators[key].append((global_step, value))
  
file_path: labml/client/labml/internal/tracker/writers/app.py
imports: import threading
  import time
  from typing import Dict
  import numpy
  from .None import Writer
  from ..indicators import Indicator
  from ..indicators.numeric import NumericIndicator
  from ...app import AppTracker, Packet, AppTrackDataSource
label_desc: Use image node_id 4 for calling the Writer obj's underlying member method code with example usage: obj._write_indicator(global_step, indicator) without return types