class_docstr: Encapsulate features, labels, and metadata for a given dataset.
  
  Parameters
  ----------
  name : str
      The name of this feature set.
  
  ids : Union[List[str], numpy.ndarray]
      Example IDs for this set.
  
  labels : Optional[Union[List[str], numpy.ndarray], default=None
      Labels for this set.
  
  features : Optional[Union[:class:`skll.types.FeatureDictList`, :class:`numpy.ndarray`]], default=None
      The features for each instance represented as either a
      list of dictionaries or a numpy array (if ``vectorizer`` is
      also specified).
  
  vectorizer : Optional[Union[:class:`sklearn.feature_extraction.DictVectorizer`, :class:`sklearn.feature_extraction.FeatureHasher`], default=None
      Vectorizer which will be used to generate the feature matrix.
  
  Warnings
  --------
  FeatureSets can only be equal if the order of the instances is
  identical because these are stored as lists/arrays. Since scikit-learn's
  ``DictVectorizer`` automatically sorts the underlying feature matrix
  if it is sparse, we do not do any sorting before checking for equality.
  This is not a problem because we _always_ use sparse matrices with
  ``DictVectorizer`` when creating FeatureSets.
  
  Notes
  -----
  If ids, labels, and/or features are not None, the number of rows in
  each array must be equal.
docstr: Return a string representation of ``FeatureSet``.
  
  Returns
  -------
  str:
      A string representation of ``FeatureSet``.
docstr_tok: ["Return","a","string","representation","of","``","FeatureSet","``",".","Returns","--","--","--","-","str",":","A","string","representation","of","``","FeatureSet","``","."]
code: def __str__(self):
      """
      Return a string representation of ``FeatureSet``.
  
      Returns
      -------
      str:
          A string representation of ``FeatureSet``.
      """
      return str(self.__dict__)
  
imports: from copy import deepcopy
  from typing import Collection, List, Optional, Tuple, Union
  import numpy
  import scipy.sparse
  from pandas import DataFrame
  from sklearn.feature_extraction import DictVectorizer, FeatureHasher
  from skll.data.dict_vectorizer import DictVectorizer
  from skll.types import FeatGenerator, FeatureDictList, IdType, LabelType, SparseFeatureMatrix
label_desc: Use image node_id 11 for calling the FeatureSet obj's underlying member method code with example usage: obj.__str__() and returns: str