Generate overlays after offset.
        :param text: The text to be searched.
        :param offset: Match starting that index. If none just search.
        :returns: An overlay or None

def offset_overlays(self, text, offset=0, **kw):
        """
        Generate overlays after offset.
        :param text: The text to be searched.
        :param offset: Match starting that index. If none just search.
        :returns: An overlay or None
        """

        # This may be a bit slower but overlayedtext takes care of
        # unicode issues.
        if not isinstance(text, OverlayedText):
            text = OverlayedText(text)

        for m in self.regex.finditer(unicode(text)[offset:]):
            yield Overlay(text, (offset + m.start(), offset + m.end()),
                          props=self.props,
                          value=self.value(rxmatch=m))