@Override
  public void writeMapBegin(TMap map) throws TException {
    // nesting not allowed!
    if (map.keyType == TType.STRUCT || map.keyType == TType.MAP
        || map.keyType == TType.LIST || map.keyType == TType.SET) {
      throw new TException("Not implemented: nested structures");
    }
    // nesting not allowed!
    if (map.valueType == TType.STRUCT || map.valueType == TType.MAP
        || map.valueType == TType.LIST || map.valueType == TType.SET) {
      throw new TException("Not implemented: nested structures");
    }

    firstInnerField = true;
    isMap = true;
    inner = true;
    elemIndex = 0;
  }
Initialize the TProtocol.

@param conf
         System properties
@param tbl
         table properties
@throws TException
serde/src/java/org/apache/hadoop/hive/serde2/thrift/TCTLSeparatedProtocol.java