def repo_exists(github_repos, repo_slug):
    """Checks if a repository with a given slug exists among the public GitHub repositories.

    Args:
     - github_repos: List of GitHub repositories.
     - repo_slug: Repository slug (usually in a form of path with a namespace, eg: "username/reponame").

    Returns:
     - True if repository exists, False otherwise.
    """

    return any(repo['full_name'] == repo_slug for repo in github_repos)