def get_examples(self, indices, key_indices):
    'Return a part of data.\n\n        Args:\n            indices (list of ints or slice): Indices of requested rows.\n                If this argument is :obj:`None`, it indicates all rows.\n            key_indices (tuple of ints): Indices of requested columns.\n                If this argument is :obj:`None`, it indicates all columns.\n\n        Returns:\n            tuple of lists/arrays\n        '
    raise NotImplementedError
Return a part of data.

Args:
    indices (list of ints or slice): Indices of requested rows.
        If this argument is :obj:`None`, it indicates all rows.
    key_indices (tuple of ints): Indices of requested columns.
        If this argument is :obj:`None`, it indicates all columns.

Returns:
    tuple of lists/arrays
def get_examples(self, indices, key_indices):
    'Return a part of data.\n\n        Args:\n            indices (list of ints or slice): Indices of requested rows.\n                If this argument is :obj:`None`, it indicates all rows.\n            key_indices (tuple of ints): Indices of requested columns.\n                If this argument is :obj:`None`, it indicates all columns.\n\n        Returns:\n            tuple of lists/arrays\n        '
    raise NotImplementedError