docs: def initialize(self, session=None, force=False):
          """
          Initializes TensorFlow variables, which are returned by `initializables` property and
          uses feed dictionary returned by `initializable_feeds` property defined at ICompilable
          interface and implemented by descendants.
  
          :param session: TensorFlow session used for initializing. In case when session is None,
              default TensorFlow session will be checked first, if session is still None, then
              default GPflowFlow session will used, but there is *no garuantee* that GPflow
              session's graph is compliant with node's tensors graph.
          :param force: inidicates either the initialized TensorFlow variables must be
              re-initialized or not.
  
          :raises: GPflowError exception if session's graph is different from the graph
              used by node tensors.
          """
          session = self.enquire_session(session)
          initializables = self.initializables
          if initializables:
              misc.initialize_variables(
                  variables=initializables,
                  session=session,
                  force=force,
                  feed_dict=self.initializable_feeds)