docs: def features_keep_within_radius(obj, center, radius, units):
      """
      Filter all features in a collection by retaining only those that
      fall within the specified radius.
      """
      features_keep = []
      for feature in tqdm(obj['features']):
          if all([getattr(geopy.distance.vincenty((lat,lon), center), units) < radius for (lon,lat) in geojson.utils.coords(feature)]):
              features_keep.append(feature)
      obj['features'] = features_keep
      return obj