<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def getUser(self):
 """Returns the linked Plone User or None """

        username = self.getUsername()
        if not username:
            return None
        user = api.user.get(userid=username)
        return user