code: void assignToNew(String fileName, PageFormatter fmtr) {
  		internalLock.writeLock().lock();
  		try {
  			flush();
  			fmtr.format(this);
  			blk = contents.append(fileName);
  			pins = 0;
  			isNew = true;
  			lastLsn = LogSeqNum.DEFAULT_VALUE;
  		} finally {
  			internalLock.writeLock().unlock();
  		}
  	}
docs: Initializes the buffer's page according to the specified formatter, and
  appends the page to the specified file. If the buffer was dirty, then the
  contents of the previous page are first written to disk.
  
  @param filename
  the name of the file
  @param fmtr
  a page formatter, used to initialize the page