There are a couple of ways to reset the image to it's original state. In the develop module the bottom right button of the right column will reset the image and remove all edits. If you want to reset some of the edits you can double click on the center of any of the sliders and the values will be reset.
Thanks! Yes, I use these methods. But I'm interested in resetting via script. I tried to use the photo:applyDevelopPreset(preset, _PLUGIN). But I can not find values in the preset that would be universal for all photos