Script to skip frames with no animation

Question

I found a script (here: Can frames with no animation be automatically skipped?) that should do exactly what I need. But When I add it to the text editor and press run in Blender it does nothing. How do I get it running please? (I really have no clue how codes work, so explaining it to me like to an idiot would be very much appreciated.)

import bpy
import subprocess
import os
import shutil
def render_with_skips(start, stop):
    """
    Take start and stop, and render animation only for animated
    frames. Still frames, are substituted into the output folder
    as copies of their equivalents.
    """
render_range = list(range(start, stop))

# create JSON like dictionary to store each
# animated object's fcurve data at each frame.
all_obj_fcurves = {}
for obj in bpy.data.objects:    
    obj_fcurves = {}

    try:
        obj.animation_data.action.fcurves
    except AttributeError:
        print("--|'%s' is not animated" % obj.name)
        continue

    print("\n--> '%s' is animated at frames:" % obj.name)

    for fr in list(range(start,stop+1)):
        fc_evals = [c.evaluate(fr) for c in obj.animation_data.action.fcurves]
        obj_fcurves.update({int(fr): fc_evals})
        print(fr, end=", ")
    print()

    all_obj_fcurves.update({obj.name: obj_fcurves})


# loop through each animated object and find its
# animated frames. then remove those frames from
# a set containing all frames, to get still frames.
still_frames = set(render_range)
for obj in all_obj_fcurves.keys():
    obj_animated_frames = []
    for i, fr in enumerate(sorted(all_obj_fcurves[obj].keys())):
        if i != 0:
            if all_obj_fcurves[obj][fr] != all_obj_fcurves[obj][fr_prev]:
                obj_animated_frames.append(fr)
        fr_prev = fr

    still_frames = still_frames - set(obj_animated_frames)

print("\nFound %d still frames" % len(still_frames))
print(sorted(still_frames), end="\n\n")


# render animation, skipping the still frames and
# filling them in as copies of their equivalents
filepath = bpy.context.scene.render.filepath

for fr in render_range:
    if fr not in still_frames or fr == render_range[0]:
        bpy.context.scene.frame_set(fr)
        bpy.context.scene.render.filepath = filepath + '%04d' % fr
        bpy.ops.render.render(write_still=True)
    else:
        scene = bpy.context.scene
        abs_filepath = scene.render.frame_path(scene.frame_current)
        #abs_path = '/'.join(abs_filepath.split('/')[:-1]) + '/'
        print("Frame %d is still, copying from equivalent" % fr)
        scn = bpy.context.scene
        shutil.copyfile(filepath + '%04d.png' % (fr-1), filepath + '%04d.png' % fr)

bpy.context.scene.render.filepath = filepath


start = bpy.data.scenes['Scene'].frame_start
end = bpy.data.scenes['Scene'].frame_end
render_with_skips(start,end)
```