@abstractmethod<EOL><INDENT>def _augment_heatmaps(self, heatmaps, random_state, parents, hooks):<DEDENT>
raise NotImplementedError()<EOL>
Augment heatmaps on multiple images.

This is the internal version of ``augment_heatmaps()``.
It is called from ``augment_heatmaps()`` and should usually not be called
directly.
This method may heatmaps in-place.
This method does not have to care about determinism or the
Augmenter instance's ``random_state`` variable. The parameter
``random_state`` takes care of both of these.

Parameters
----------
heatmaps : list of imgaug.HeatmapsOnImage
    Heatmaps to augment. They may be changed in-place.

parents : list of imgaug.augmenters.meta.Augmenter
    See :func:`imgaug.augmenters.meta.Augmenter.augment_heatmaps`.

hooks : imgaug.HooksHeatmaps or None
    See :func:`imgaug.augmenters.meta.Augmenter.augment_heatmaps`.

Returns
----------
images : list of imgaug.HeatmapsOnImage
    The augmented heatmaps.