public ParseResult parse(String command) throws ParseException {
    return parse(command, null);
  }
Creates an ASTNode for the given token. The ASTNode is a wrapper around
antlr's CommonTree class that implements the Node interface.

@param payload
         The token.
@return Object (which is actually an ASTNode) for the token.
parser/src/java/org/apache/hadoop/hive/ql/parse/ParseDriver.java