'Constructor.
Args:
stream: (io.Base, file object), the stream to wrap.
begin: int, the seek position the chunk begins at.
chunksize: int, the size of the chunk.'

def __init__(self, stream, begin, chunksize):

    self._stream = stream
    self._begin = begin
    self._chunksize = chunksize
    self._stream.seek(begin)
