class_docstr: A batch of Instances. In addition to containing the instances themselves,
  it contains helper functions for converting the data into tensors.
  
  A Batch just takes an iterable of instances in its constructor and hangs onto them
  in a list.
class_docstr_tok: ["A","batch","of","Instances",".","In","addition","to","containing","the","instances","themselves",",","it","contains","helper","functions","for","converting","the","data","into","tensors",".","A","Batch","just","takes","an","iterable","of","instances","in","its","constructor","and","hangs","onto","them","in","a","list","."]
code: def print_statistics(self) -> None:
      # Make sure if has been indexed first
      sequence_field_lengths: Dict[str, List] = defaultdict(list)
      for instance in self.instances:
          if not instance.indexed:
              raise ConfigurationError(
                  "Instances must be indexed with vocabulary "
                  "before asking to print dataset statistics."
              )
          for (
              field,
              field_padding_lengths,
          ) in instance.get_padding_lengths().items():
              for key, value in field_padding_lengths.items():
                  sequence_field_lengths[f"{field}.{key}"].append(value)
  
      print("\n\n----Dataset Statistics----\n")
      for name, lengths in sequence_field_lengths.items():
          print(f"Statistics for {name}:")
          print(
              f"\tLengths: Mean: {numpy.mean(lengths)}, Standard Dev: {numpy.std(lengths)}, "
              f"Max: {numpy.max(lengths)}, Min: {numpy.min(lengths)}"
          )
  
      print("\n10 Random instances:")
      for i in numpy.random.randint(len(self.instances), size=10):
          print(f"Instance {i}:")
          print(f"\t{self.instances[i]}")
  
file_path: allennlp/allennlp/data/batch.py
imports: import logging
  from collections import defaultdict, Counter
  from typing import Dict, Iterable, Iterator, List, Union
  import numpy
  import torch
  from allennlp.common.checks import ConfigurationError
  from allennlp.common.util import ensure_list
  from allennlp.data.instance import Instance
  from allennlp.data.vocabulary import Vocabulary
label_desc: Use image node_id 7 for calling the Batch obj's underlying member method code with example usage: obj.print_statistics() without return types