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

def build_from_file(self, dockerfile, tag, **kwargs):
        """
        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
        """
        with DockerContext(dockerfile, finalize=True) as ctx:
            return self.build_from_context(ctx, tag, **kwargs)