'Creates an instance of the InputReader for the given input shard state.
Args:
json: The InputReader state as a dict-like object.
Returns:
An instance of the InputReader configured using the values of json.'

@classmethod
def from_json(cls, json):

    return cls(json[cls.BLOB_KEY_PARAM], json[cls.START_INDEX_PARAM], json[cls.END_INDEX_PARAM])
