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: substitute_wildcards.rs
    path of file: ./repos/nickel/core/src/transform
    
    the code of the file until where you have to start completion: //! Substitute wildcard types with their inferred type.
//!
//! During type checking, wildcard types are treated as type variables that may end up unified
//! with a concrete type.  
    
    fn subst_wildcards(self, wildcards: &Wildcards) -> TypeAnnotation {
        let typ = self
            .typ
            .map(|labeled_ty| labeled_ty.subst_wildcards(wildcards));
        let contracts = self
            .contracts
            .into_iter()
            .map(|labeled_ty| labeled_ty.subst_wildcards(wildcards))
            .collect();

        TypeAnnotation { typ, contracts }
    }