code: def get_authentication_header(self, user=None, api_key=None, password=None, certificate=None):
          
  
          if not user:
              user = self.user
  
          if not api_key:
              api_key = self.api_key
  
          if not password:
              password = self.password
  
          if not password:
              password = self.password
  
          if not certificate:
              certificate = self._certificate
  
          if certificate:
              return "XREST %s" % urlsafe_b64encode("{}:".format(user).encode('utf-8')).decode('utf-8')
  
          if api_key:
              return "XREST %s" % urlsafe_b64encode("{}:{}".format(user, api_key).encode('utf-8')).decode('utf-8')
  
  
          return "XREST %s" % urlsafe_b64encode("{}:{}".format(user, password).encode('utf-8')).decode('utf-8')
docs: Return authenication string to place in Authorization Header
  
              If API Token is set, it'll be used. Otherwise, the clear
              text password will be sent. Users of NURESTLoginController are responsible to
              clean the password property.
  
              Returns:
                  Returns the XREST Authentication string with API Key or user password encoded.