'Seek to specified position into the chunk.
Default position is 0 (start of chunk).
If the file is not seekable, this will result in an error.'

def seek(self, pos, whence=0):

    if self.closed:
        raise ValueError, 'I/O    operation    on    closed    file'
    if (not self.seekable):
        raise IOError, 'cannot    seek'
    if (whence == 1):
        pos = (pos + self.size_read)
    elif (whence == 2):
        pos = (pos + self.chunksize)
    if ((pos < 0) or (pos > self.chunksize)):
        raise RuntimeError
    self.file.seek((self.offset + pos), 0)
    self.size_read = pos
