code: def get_mosaic_epoch_size(num_workers, target_worker_gb=10):
      if target_worker_gb == -1:
          return None
      AVG_MOSAIC_IMAGE_SIZE_BYTES = 500 * 1024  # 500KiB.
      epoch_size = math.ceil(
          target_worker_gb
          * num_workers
          * 1024
          * 1024
          * 1024
          / AVG_MOSAIC_IMAGE_SIZE_BYTES
      )
      return epoch_size
  
imports: import math
label_desc: Use image node_id 4 for calling a global function with example usage: get_mosaic_epoch_size(num_workers, target_worker_gb) and returns: epoch_size, None