'Constructor.
Args:
blob_key: The blob key or string blob key to read from.
buffer_size: The minimum size to fetch chunks of data from blobstore.
position: The initial position in the file.'

def __init__(self, blob_key, buffer_size=131072, position=0):

    self.__blob_key = blob_key
    self.__buffer_size = buffer_size
    self.__buffer = ''
    self.__position = position
    self.__buffer_position = 0
    self.__eof = False
    self.__blob_info = None
