old_contents: from lib import action
  
  class BuildProject(action.JenkinsBaseAction):
      def run(self, project, branch="master"):
          return self.jenkins.build_job(project, {'branch': branch})
  
new_contents: from lib import action
  
  
  class BuildProject(action.JenkinsBaseAction):
      def run(self, project, branch="master"):
          return self.jenkins.build_job(project, {'branch': branch})
  
subject: Update build_job.py