Warnings when discarding segments during windowing

[tmgdejong]

When calling the function discard_segments from windowing.py, the following warnings appear:

[...]/paradigma/windowing.py:212: SettingWithCopyWarning: 
A value is trying to be set on a copy of a slice from a DataFrame.
Try using .loc[row_indexer,col_indexer] = value instead

See the caveats in the documentation: https://pandas.pydata.org/pandas-docs/stable/user_guide/indexing.html#returning-a-view-versus-a-copy
  df.loc[df[segment_nr_colname]==segment_nr, f'{segment_nr_colname}_ordered'] = np.where(df[segment_nr_colname].unique()==segment_nr)[0][0] + 1

[...]/paradigma/windowing.py:214: SettingWithCopyWarning: 
A value is trying to be set on a copy of a slice from a DataFrame.
Try using .loc[row_indexer,col_indexer] = value instead

See the caveats in the documentation: https://pandas.pydata.org/pandas-docs/stable/user_guide/indexing.html#returning-a-view-versus-a-copy
  df[f'{segment_nr_colname}_ordered'] = df[f'{segment_nr_colname}_ordered'].astype(int)