[QST] Is there a way to do custom aggregations?

For example I want to get the total progress within a group. My code looks like:

cols = ["user", "timecode", "published_at"]

aggs = {
        'timecode': ["first", "last"],
}

usages = cols >> nvt.ops.Groupby(
    groupby_cols="user"
    sort_cols=["published_at"],
    aggs=aggs,
    name_sep="_")

dataset = nvt.Dataset(data)
workflow = nvt.Workflow(all_feats)
sessions_gdf = workflow.fit_transform(dataset).to_ddf()
sessions_gdf["progress"] = sessions_gdf.progress_last - sessions_gdf.progress_first

Is there a way to include the subtraction into the workflow? I tested a couple of things like:

aggs = {
        'progress': [nvt.ops.LambdaOp(lambda col: col.last() - col.first())],
}

or

aggs = {
        'progress': [lambda col: col.last() - col.first()]
}

but neither seems to be supported. Is there another way to express this?

[krlng]

Thanks, that looks great, will try that!

[rnyak]

@krlng is the workaround above works for you? can we close this issue? thanks.