code: def package_installed(package_name, service_name=None):
      
  
      package_manager = _get_package_manager()
  
      app_installed = len(package_manager.installed_apps(package_name, service_name)) > 0
  
      subcommand_installed = False
      for subcmd in package.installed_subcommands():
          package_json = subcmd.package_json()
          if package_json['name'] == package_name:
              subcommand_installed = True
  
      return (app_installed or subcommand_installed)
docs: Check whether the package package_name is currently installed.
  
          :param package_name: package name
          :type package_name: str
          :param service_name: service_name
          :type service_name: str
  
          :return: True if installed, False otherwise
          :rtype: bool