How to use the ufo2ft.featureWriters.ast.MarkClassDefinition function in ufo2ft

if accentName in markClass.glyphs:
                mcdef = markClass.glyphs[accentName]
                if cls._anchorsAreEqual(anchor, mcdef.anchor):
                    logger.debug(
                        "Glyph %s already defined in markClass @%s",
                        accentName,
                        className,
                    )
                    return None
                else:
                    # same accent glyph defined with different anchors for the
                    # same markClass; make a new unique markClass definition
                    newClassName = ast.makeFeaClassName(className, markClasses)
                    markClass = ast.MarkClass(newClassName)
                    markClasses[newClassName] = markClass
        mcdef = ast.MarkClassDefinition(markClass, anchor, glyphs)
        markClass.addDefinition(mcdef)
        return mcdef

mcdef = markClass.glyphs[glyphName]
                if self._anchorsAreEqual(anchor, mcdef.anchor):
                    self.log.debug(
                        "Glyph %s already defined in markClass @%s",
                        glyphName,
                        className,
                    )
                    return None
                else:
                    # same mark glyph defined with different anchors for the
                    # same markClass; make a new unique markClass definition
                    newClassName = ast.makeFeaClassName(className, markClasses)
                    markClass = ast.MarkClass(newClassName)
                    markClasses[newClassName] = markClass
        glyphName = ast.GlyphName(glyphName)
        mcdef = ast.MarkClassDefinition(markClass, anchor, glyphName)
        markClass.addDefinition(mcdef)
        return mcdef