如何在Gtk SourceView中使用自定义语言突出显示语法？

<?xml version="1.0" encoding="UTF-8"?>
<language id="mylanguage" _name="My Language" version="1.0" _section="Sources">
  <metadata>
    <property name="mimetypes">text/x-mylanguage</property>
    <property name="globs">*.mylang</property>
  </metadata>
  <styles>
    <style id="keyword" _name="Keyword" map-to="def:keyword"/>
    <style id="comment" _name="Comment" map-to="def:comment"/>
    <style id="string" _name="String" map-to="def:string"/>
    <style id="number" _name="Number" map-to="def:number"/>
  </styles>
  <definitions>
    <context id="main" style-ref="keyword">
      <keyword>if</keyword>
      <keyword>else</keyword>
      <keyword>while</keyword>
      <!-- 其他关键字 -->
    </context>
    <context id="comment" style-ref="comment">
      <start>/\*</start>
      <end>\*/</end>
    </context>
    <context id="string" style-ref="string">
      <start>"</start>
      <end>"</end>
    </context>
    <context id="number" style-ref="number">
      <start>\b\d+(\.\d+)?\b</start>
    </context>
  </definitions>
</language>

import gi
gi.require_version('Gtk', '3.0')
gi.require_version('GtkSource', '3.0')
from gi.repository import Gtk, GtkSource

def main():
    # 创建窗口和布局
    window = Gtk.Window()
    window.set_default_size(600, 400)
    layout = Gtk.Box(orientation=Gtk.Orientation.VERTICAL)
    window.add(layout)

    # 创建SourceView对象
    sourceview = GtkSource.View()

    # 设置SourceView的属性
    sourceview.set_show_line_numbers(True)
    sourceview.set_auto_indent(True)

    # 创建SourceBuffer对象并加载文件内容
    buffer = sourceview.get_buffer()
    with open('myfile.mylang', 'r') as file:
        text = file.read()
        buffer.set_text(text)

    # 创建SourceLanguageManager对象并加载自定义语言定义文件
    manager = GtkSource.LanguageManager()
    language = manager.get_language('mylanguage')
    buffer.set_language(language)

    # 将SourceView添加到布局中
    layout.pack_start(sourceview, True, True, 0)

    # 显示窗口
    window.show_all()
    Gtk.main()

if __name__ == '__main__':
    main()