parquet-thrift/src/main/java/org/apache/parquet/thrift/ThriftMetaData.java
public Map<String, String> toExtraMetaData() {
    final Map<String, String> map = new HashMap<String, String>();
    map.put(THRIFT_CLASS, getThriftClass().getName());
    map.put(THRIFT_DESCRIPTOR, descriptor.toJSON());
    return map;
  }
public Map<String, String> toExtraMetaData() {
    final Map<String, String> map = new HashMap<String, String>();
    map.put(THRIFT_CLASS, getThriftClass().getName());
    map.put(THRIFT_DESCRIPTOR, descriptor.toJSON());
    return map;
  }
generates a map of key values to store in the footer
@return the key values