class_docstr: Base class for loading datasets.
  
  Note that you should never instantiate the :class:`Dataset` class directly
  (same goes for its derived classes), but instead use one of the three
  available methods for loading datasets.
docstr: Load a dataset from a (custom) file.
  
  Use this if you want to use a custom dataset and all of the ratings are
  stored in one file. You will have to split your dataset using the
  :meth:`split <DatasetAutoFolds.split>` method. See an example in the
  :ref:`User Guide <load_from_file_example>`.
  
  
  Args:
      file_path(:obj:`string`): The path to the file containing ratings.
      reader(:obj:`Reader <surprise.reader.Reader>`): A reader to read
          the file.
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code: def load_from_file(cls, file_path, reader):
      """Load a dataset from a (custom) file.
  
      Use this if you want to use a custom dataset and all of the ratings are
      stored in one file. You will have to split your dataset using the
      :meth:`split <DatasetAutoFolds.split>` method. See an example in the
      :ref:`User Guide <load_from_file_example>`.
  
  
      Args:
          file_path(:obj:`string`): The path to the file containing ratings.
          reader(:obj:`Reader <surprise.reader.Reader>`): A reader to read
              the file.
      """
  
      return DatasetAutoFolds(ratings_file=file_path, reader=reader)
  
imports: import itertools
  import os
  import sys
  from collections import defaultdict
  from .builtin_datasets import BUILTIN_DATASETS, download_builtin_dataset
  from .reader import Reader
  from .trainset import Trainset
label_desc: Use image node_id 3 for calling the Dataset obj's underlying member method code with example usage: obj.load_from_file(cls, file_path, reader) and returns: DatasetAutoFolds