Subclasses may override this method.

def _appendGlyph(self, other, offset=None):
        """
        Subclasses may override this method.
        """
        other = other.copy()
        if offset != (0, 0):
            other.moveBy(offset)
        for contour in other.contours:
            self.appendContour(contour)
        for component in other.components:
            self.appendComponent(component=component)
        for anchor in other.anchors:
            self.appendAnchor(anchor=anchor)
        for guideline in other.guidelines:
            self.appendGuideline(guideline=guideline)