def get_extra_mimetypes():
    """Augment the Mimeview system with new mimetypes associations.

        This is an optional method. Not implementing the method or
        returning nothing is fine, the component will still be asked
        via `get_quality_ratio` if it supports a known mimetype.  But
        implementing it can be useful when the component knows about
        additional mimetypes which may augment the list of already
        mimetype to keywords associations.

        Generate ``(mimetype, keywords)`` pairs for each additional
        mimetype, with ``keywords`` being a list of keywords or
        extensions that can be used as aliases for the mimetype
        (typically file suffixes or Wiki processor keys).

        .. versionadded:: 1.0
        """
