docs: def features_properties_null_remove(obj):
      """
      Remove any properties of features in the collection that have 
      entries mapping to a null (i.e., None) value
      """
      features = obj['features']
      for i in tqdm(range(len(features))):
          if 'properties' in features[i]:
              properties = features[i]['properties']
              features[i]['properties'] = {p:properties[p] for p in properties if properties[p] is not None}
      return obj