parquet-hadoop/src/main/java/org/apache/parquet/hadoop/ParquetFileWriter.java
static MessageType mergeInto(MessageType toMerge, MessageType mergedSchema) {
    return mergeInto(toMerge, mergedSchema, true);
  }
static MessageType mergeInto(MessageType toMerge, MessageType mergedSchema) {
    return mergeInto(toMerge, mergedSchema, true);
  }
will return the result of merging toMerge into mergedSchema
@param toMerge the schema to merge into mergedSchema
@param mergedSchema the schema to append the fields to
@return the resulting schema