def get_available_tf_versions(include_prerelease=False):
    """Return available Terraform versions."""
    tf_releases = json.loads(
        requests.get('https://releases.hashicorp.com/index.json').text
    )['terraform']
    tf_versions = sorted([k  # descending
                          for k, _v in tf_releases['versions'].items()],
                         key=LooseVersion,
                         reverse=True)
    if include_prerelease:
        return tf_versions
    return [i for i in tf_versions if '-' not in i]
Return available Terraform versions.