class_docstr: TFTrainer is a simple but feature-complete training and eval loop for TensorFlow, optimized for 🤗 Transformers.
  
  Args:
      model ([`TFPreTrainedModel`]):
          The model to train, evaluate or use for predictions.
      args ([`TFTrainingArguments`]):
          The arguments to tweak training.
      train_dataset ([`~tf.data.Dataset`], *optional*):
          The dataset to use for training. The dataset should yield tuples of `(features, labels)` where `features`
          is a dict of input features and `labels` is the labels. If `labels` is a tensor, the loss is calculated by
          the model by calling `model(features, labels=labels)`. If `labels` is a dict, such as when using a
          QuestionAnswering head model with multiple targets, the loss is instead calculated by calling
          `model(features, **labels)`.
      eval_dataset ([`~tf.data.Dataset`], *optional*):
          The dataset to use for evaluation. The dataset should yield tuples of `(features, labels)` where `features`
          is a dict of input features and `labels` is the labels. If `labels` is a tensor, the loss is calculated by
          the model by calling `model(features, labels=labels)`. If `labels` is a dict, such as when using a
          QuestionAnswering head model with multiple targets, the loss is instead calculated by calling
          `model(features, **labels)`.
      compute_metrics (`Callable[[EvalPrediction], Dict]`, *optional*):
          The function that will be used to compute metrics at evaluation. Must take a [`EvalPrediction`] and return
          a dictionary string to metric values.
      tb_writer (`tf.summary.SummaryWriter`, *optional*):
          Object to write to TensorBoard.
      optimizers (`Tuple[tf.keras.optimizers.Optimizer, tf.keras.optimizers.schedules.LearningRateSchedule]`, *optional*):
          A tuple containing the optimizer and the scheduler to use. The optimizer default to an instance of
          [`tf.keras.optimizers.Adam`] if `args.weight_decay_rate` is 0 else an instance of [`AdamWeightDecay`]. The
          scheduler will default to an instance of [`tf.keras.optimizers.schedules.PolynomialDecay`] if
          `args.num_warmup_steps` is 0 else an instance of [`WarmUp`].
code: def _compute_nb_instances(batch):
      labels = batch[-1]
      if isinstance(labels, PerReplica):
          labels = tf.concat(labels.values, axis=0)
  
      nb_instances = tf.reduce_sum(
          tf.cast(labels != -100, dtype=tf.int32)
      )
  
      return nb_instances
  
imports: import datetime
  import math
  import os
  import warnings
  from typing import Callable, Dict, Optional, Tuple
  from .utils import ENV_VARS_TRUE_VALUES
  from .integrations import is_comet_available, is_wandb_available
  import numpy
  import tensorflow
  from tensorflow.python.distribute.values import PerReplica
  from .modeling_tf_utils import TFPreTrainedModel
  from .optimization_tf import GradientAccumulator, create_optimizer
  from .trainer_utils import PREFIX_CHECKPOINT_DIR, EvalPrediction, IntervalStrategy, PredictionOutput, enable_full_determinism, set_seed
  from .training_args_tf import TFTrainingArguments
  from .utils import logging
label_desc: Use image node_id 17 for calling the TFTrainer obj's underlying member method code with example usage: obj._compute_nb_instances(batch) and returns: nb_instances