code: def get_user(user_or_username=None):
      
      if user_or_username is None:
          return None
      if hasattr(user_or_username, "getUserId"):
          return ploneapi.user.get(user_or_username.getUserId())
      return ploneapi.user.get(userid=u.to_string(user_or_username))
docs: Return Plone User
  
      :param user_or_username: Plone user or user id
      :type groupname:  PloneUser/MemberData/str
      :returns: Plone MemberData
      :rtype: object