<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def checkout_default_branch(self):
 """ git checkout default branch """

        set_state(WORKFLOW_STATES.CHECKING_OUT_DEFAULT_BRANCH)

        cmd = "git", "checkout", self.config["default_branch"]
        self.run_cmd(cmd)

        set_state(WORKFLOW_STATES.CHECKED_OUT_DEFAULT_BRANCH)