code: def update(self, user, name=None, password=None, host=None):
          
          if not any((name, password, host)):
              raise exc.MissingDBUserParameters("You must supply at least one of "
                      "the following: new username, new password, or new host "
                      "specification.")
          if not isinstance(user, CloudDatabaseUser):
              # Must be the ID/name
              user = self.get(user)
          dct = {}
          if name and (name != user.name):
              dct["name"] = name
          if host and (host != user.host):
              dct["host"] = host
          if password:
              dct["password"] = password
          if not dct:
              raise exc.DBUpdateUnchanged("You must supply at least one changed "
                      "value when updating a user.")
          uri = "/%s/%s" % (self.uri_base, user.name)
          body = {"user": dct}
          resp, resp_body = self.api.method_put(uri, body=body)
          return None
docs: Allows you to change one or more of the user's username, password, or
          host.