You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: win.rs
    path of file: ./repos/tremor-runtime/tremor-script/src/std_lib
    
    the code of the file until where you have to start completion: // Copyright 2020-2021, The Tremor Team
//
// Licensed under the 
    
    fn merge(&mut self, src: &dyn TremorAggrFn) -> FResult<()> {
        // On self is earlier then other, so we don't do anything unless
        // we had no value
        if let Some(other) = src.downcast_ref::<Self>() {
            if self.0.is_none() {
                self.0 = other.0.clone();
            }
        }
        Ok(())
    }