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: dataframe.rs
    path of file: ./repos/Peroxide/src/structure
    
    the code of the file until where you have to start completion: //! Pandas-like dataframe & series.
//!
//! ## Series
//!
//! ### 1. Declare Series
//!
//! * To declare series, you should have `Vec<T>` where `T` is one of following types.
//!
//! | Primitive 
    
    fn sub_vec<'a, 'b>(&'a self, rhs: &'b Self) -> Self {
        assert_eq!(self.dtype, rhs.dtype, "DTypes are not same (add_vec)");
        dtype_match!(
            N;
            self.dtype,
            self.to_vec(),
            |x| sub_vec(x, rhs.to_vec());
            Vec
        )
    }