def registerHandler(self, fh): 
self.fds.add(fh)<EOL>self.atime = int(time()) <EOL>self.lock.acquire()<EOL>try:<EOL><INDENT>if (<NUM_LIT:0>, self.filesize) not in self.avail and self.preferences['<STR_LIT>'] is False:<EOL><INDENT>Downloader.fetch(self, None, fh) <EOL><DEDENT><DEDENT>except requests.exceptions.ConnectionError:<EOL><INDENT>raise ConnectionError<EOL><DEDENT>finally:<EOL><INDENT>self.lock.release()<EOL><DEDENT>
Register new file descriptor.

Parameters
----------
fh : int
    File descriptor.