class_docstr: Batcher designed to batch rows of data, before padding.
code: def from_config(cls, config: Config):
      return cls(
          config.train_batch_size,
          config.eval_batch_size,
          config.test_batch_size,
      )
  
imports: import functools
  import itertools
  import math
  import random
  from typing import Any, Dict, Iterable, List, MutableMapping, NamedTuple, Optional, Type
  from pytext.common.constants import RawExampleFieldName, Stage
  from pytext.config.component import Component, ComponentType, create_component, Registry
  from pytext.utils.usage import log_class_usage
  from .sources import DataSource, RawExample, TSVDataSource
  from .sources.data_source import GeneratorIterator, RowShardedDataSource, ShardedDataSource
  from .tensorizers import initialize_tensorizers, MetricTensorizer, Tensorizer
label_desc: Use image node_id 1 for calling the Batcher obj's underlying member method code with example usage: obj.from_config(cls, config) and returns: cls