code: def build_from_file(self, dockerfile, tag, **kwargs):
          
          with DockerContext(dockerfile, finalize=True) as ctx:
              return self.build_from_context(ctx, tag, **kwargs)
docs: Builds a docker image from the given :class:`~dockermap.build.dockerfile.DockerFile`. Use this as a shortcut to
          :meth:`build_from_context`, if no extra data is added to the context.
  
          :param dockerfile: An instance of :class:`~dockermap.build.dockerfile.DockerFile`.
          :type dockerfile: dockermap.build.dockerfile.DockerFile
          :param tag: New image tag.
          :type tag: unicode | str
          :param kwargs: See :meth:`docker.client.Client.build`.
          :return: New, generated image id or ``None``.
          :rtype: unicode | str