code: public static UpdateDescription fromBsonDocument(final BsonDocument document) {
      keyPresent(Fields.UPDATED_FIELDS_FIELD, document);
      keyPresent(Fields.REMOVED_FIELDS_FIELD, document);
  
      final BsonArray removedFieldsArr =
          document.getArray(Fields.REMOVED_FIELDS_FIELD);
      final Set<String> removedFields = new HashSet<>(removedFieldsArr.size());
      for (final BsonValue field : removedFieldsArr) {
        removedFields.add(field.asString().getValue());
      }
  
      return new UpdateDescription(document.getDocument(Fields.UPDATED_FIELDS_FIELD), removedFields);
    }
docs: Converts an update description BSON document from a MongoDB Change Event into an
  UpdateDescription object.
  
  @param document the
  @return the converted UpdateDescription