human
I wrote the below code

    api_url = build_api_url(github_slug)
    releases = []
    wf().logger.debug(u'Retrieving    releases    list    from    `{0}`    ...'.format(api_url))
    def retrieve_releases():
        wf().logger.info(u'Retrieving    releases    for    `{0}`    ...'.format(github_slug))
        return web.get(api_url).json()
    slug = github_slug.replace(u'/', u'-')
    for release in wf().cached_data(u'gh-releases-{0}'.format(slug), retrieve_releases):
        version = release[u'tag_name']
        download_urls = []
        for asset in release.get(u'assets', []):
            url = asset.get(u'browser_download_url')
            if ((not url) or (not url.endswith(u'.alfredworkflow'))):
                continue
            download_urls.append(url)
        if (release[u'prerelease'] and (not prereleases)):
            wf().logger.warning(u'Invalid    release    {0}    :    pre-release    detected'.format(version))
            continue
        if (not download_urls):
            wf().logger.warning(u'Invalid    release    {0}    :    No    workflow    file'.format(version))
            continue
        if (len(download_urls) > 1):
            wf().logger.warning(u'Invalid    release    {0}    :    multiple    workflow    files'.format(version))
            continue
        wf().logger.debug(u'Release    `{0}`    :    {1}'.format(version, url))
        releases.append({u'version': version, u'download_url': download_urls[0], u'prerelease': release[u'prerelease']})
    return releases

What's a good function header?
 ... Here's a good function header?
assistant
#Here's a good function header.

def get_valid_releases(github_slug, prereleases=False):