class_docstr: A helper class to implement a TabularDataset.
  
  This class wraps an instance of :class:`~chainer.dataset.TabularDataset`
  and provides methods of :class:`~chainer.dataset.TabularDataset`.
  This class is useful to create a custom dataset class by inheriting it.
  
  >>> import numpy as np
  >>>
  >>> from chainer.dataset import tabular
  >>>
  >>> class MyDataset(tabular.DelegateDataset):
  ...
  ...     def __init__(self):
  ...         super().__init__(tabular.from_data((
  ...             ('a', np.arange(10)),
  ...             ('b', self.get_b),
  ...             ('c', [3, 1, 4, 5, 9, 2, 6, 8, 7, 0]),
  ...             (('d', 'e'), self.get_de))))
  ...
  ...     def get_b(self, i):
  ...         return 'b[{}]'.format(i)
  ...
  ...     def get_de(self, i):
  ...         return {'d': 'd[{}]'.format(i), 'e': 'e[{}]'.format(i)}
  ...
  >>> dataset = MyDataset()
  >>> len(dataset)
  10
  >>> dataset.keys
  ('a', 'b', 'c', 'd', 'e')
  >>> dataset[0]
  (0, 'b[0]', 3, 'd[0]', 'e[0]')
  
  Args:
      dataset (chainer.dataset.TabularDataset): An underlying dataset.
code: def mode(self):
      return self.dataset.mode
  
file_path: chainer/chainer/dataset/tabular/delegate_dataset.py
imports: from chainer.dataset.tabular import tabular_dataset
label_desc: Use image node_id 4 for calling the DelegateDataset obj's underlying member method code with example usage: obj.mode() and returns: self