@SuppressWarnings("unchecked")
    public ProcessFunction<Object, TBase<?, ?>> syncFunc() {
        return (ProcessFunction<Object, TBase<?, ?>>) func;
    }
Returns the {@link ProcessFunction}.

@throws ClassCastException if this function is asynchronous
thrift/thrift0.13/src/main/java/com/linecorp/armeria/internal/common/thrift/ThriftFunction.java