'Constructs the decoder.
Args:
keys_to_features: a dictionary from TF-Example keys to either
tf.VarLenFeature or tf.FixedLenFeature instances. See tensorflow\'s
parsing_ops.py.
items_to_handlers: a dictionary from items (strings) to ItemHandler
instances. Note that the ItemHandler\'s are provided the keys that they
use to return the final item Tensors.'

def __init__(self, context_keys_to_features, sequence_keys_to_features, items_to_handlers):

    self._context_keys_to_features = context_keys_to_features
    self._sequence_keys_to_features = sequence_keys_to_features
    self._items_to_handlers = items_to_handlers
