def uncompress_file(input_file_name, file_extension, dest_dir):
    """
    
    """
    if file_extension.lower() not in ('.gz', '.bz2'):
        raise NotImplementedError("Received {} format. Only gz and bz2 "
                                  "files can currently be uncompressed."
                                  .format(file_extension))
    if file_extension.lower() == '.gz':
        fmodule = gzip.GzipFile
    elif file_extension.lower() == '.bz2':
        fmodule = bz2.BZ2File
    with fmodule(input_file_name, mode='rb') as f_compressed,\
        NamedTemporaryFile(dir=dest_dir,
                           mode='wb',
                           delete=False) as f_uncompressed:
        shutil.copyfileobj(f_compressed, f_uncompressed)
    return f_uncompressed.name