Initializes the renderer by setting up the extensions (taking a comma separated
    string or iterable of extensions). These extensions are added alongside with the
    configured always-on extensions.

    Returns a markdown renderer instance.

def initialize_renderer(extensions=None):
    """
    Initializes the renderer by setting up the extensions (taking a comma separated
    string or iterable of extensions). These extensions are added alongside with the
    configured always-on extensions.

    Returns a markdown renderer instance.
    """
    if extensions is None:
        extensions = []

    if isinstance(extensions, str):
        extensions = [extension.strip() for extension in extensions.split(',')]

    for extension in getattr(settings, 'MARKYMARK_EXTENSIONS', DEFAULT_MARKYMARK_EXTENSIONS):
        extensions.append(extension)

    return markdown.Markdown(extensions=extensions)