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: mod.rs
    path of file: ./repos/prisma-engines/query-engine/dmmf/src/ast_builders/schema_ast_builder
    
    the code of the file until where you have to start completion: mod enum_renderer;
mod field_renderer;
mod object_renderer;
mod schema_renderer;
mod type_renderer;

use crate::serialization_ast::{mappings_ast::*, schema_ast::*};
use enum_renderer::*;
use field_renderer::*;
use indexmap::map::Entry;
use object_renderer::*;
use schema::*;
use schema_renderer::*;
use std::collections::HashSet;
use type_renderer::*;

pub(crate) fn render(quer
    
    fn add_field_ref_type(&mut self, identifier: Identifier, ref_type: DmmfFieldRefType) {
        // Field ref types from the namespace
        match self.schema.field_ref_types.entry(identifier.namespace().to_owned()) {
            Entry::Occupied(mut v) => v.get_mut().push(ref_type),
            Entry::Vacant(v) => {
                v.insert(vec![ref_type]);
            }
        };

        self.mark_as_rendered(identifier);
    }