code: public static ObjectSerializer getLegacy() {
  
          ClassMapBasedObjectSerializer serializer = addCommonSerializers();
  
          serializer.addObjectSerializer(Date.class, new LegacyDateSerializer(serializer));
          serializer.addObjectSerializer(BSONTimestamp.class, new LegacyBSONTimestampSerializer(serializer));
          serializer.addObjectSerializer(Binary.class, new LegacyBinarySerializer());
          serializer.addObjectSerializer(byte[].class, new LegacyBinarySerializer());
          return serializer;
      }
docs: Returns an {@code ObjectSerializer} that mostly conforms to the strict JSON format defined in
  <a href="http://docs.mongodb.org/manual/reference/mongodb-extended-json/">extended JSON</a>, but with a few differences to keep
  compatibility with previous versions of the driver.  Clients should generally prefer {@code getStrict} in preference to this method.
  
  @return object serializer
  @mongodb.driver.manual reference/mongodb-extended-json/ MongoDB Extended JSON
  @see #getStrict()