code: def pull(self, remote=None, revision=None):
          
          remote = remote or self.remote
          # Make sure the local repository exists.
          if self.create() and (remote == self.remote or not remote):
              # Don't waste time pulling from a remote repository that we just cloned.
              logger.info("Skipping pull from default remote because we just created the local %s repository.",
                          self.friendly_name)
              return
          # Make sure there is a remote repository to pull from.
          if not (remote or self.default_pull_remote):
              logger.info("Skipping pull (no default remote is configured).")
              return
          # Check if we're about to perform a redundant pull.
          update_limit = int(os.environ.get(UPDATE_VARIABLE, '0'))
          if update_limit and self.last_updated >= update_limit:
              logger.info("Skipping pull due to update limit.")
              return
          # Pull the changes from the remote repository.
          timer = Timer()
          logger.info("Pulling changes from %s into local %s repository (%s) ..",
                      remote or "default remote", self.friendly_name, format_path(self.local))
          self.context.execute(*self.get_pull_command(remote=remote, revision=revision))
          logger.debug("Took %s to pull changes from remote %s repository.", timer, self.friendly_name)
          self.mark_updated()
docs: Pull changes from a remote repository into the local repository.
  
          :param remote: The location of a remote repository (a string or :data:`None`).
          :param revision: A specific revision to pull (a string or :data:`None`).
  
          If used in combination with :class:`limit_vcs_updates` this won't
          perform redundant updates.