public T getFuncExprNodeDesc(String udfName, T... children) throws SemanticException {
      return getFuncExprNodeDescWithUdfData(udfName, null, children);
    }
This function create an ExprNodeDesc for a UDF function given the
children (arguments). It will insert implicit type conversion functions
if necessary.

@throws UDFArgumentException
ql/src/java/org/apache/hadoop/hive/ql/parse/type/TypeCheckProcFactory.java