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/rust-protobuf/protobuf-codegen/src/customize
    
    the code of the file until where you have to start completion: pub(crate) mod ctx;
pub(crate) mod rustproto_proto;

use std::fmt;
use std::ops::Deref;
use std::rc::Rc;

use protobuf::reflect::EnumDescriptor;
use protobuf::reflect::FieldDescriptor;
use protobuf::reflect::FileDescriptor;
use protobuf::reflect::MessageDescriptor;
use protobuf::reflect::OneofDescriptor;

/// Dynamic callback to customize code generation.
pub trait CustomizeCallback: 'static {
    fn file(&self, file: &FileDescriptor) -> Customize {
        let _ = file;
        Customize::default()
    }

    fn message(&self, message: &MessageDescriptor) -> Customize {
        let _ = message;
        Customize::default()
    }

    fn field(&self, field: &FieldDescriptor) -> Customize {
        let _ = field;
        Customize::default()
    }

    fn special_field(&self, message: &MessageDescriptor, field: &str) -> Customize {
        let _ = (message, field);
        Customize::default()
    }

    fn enumeration(&self, enum_type: &EnumDescriptor) -> Customize {
        let _ = enum_type;
        Customize::default()
    }

    fn oneof(&self, oneof: &OneofDescriptor) -> Customize {
        let _ = oneof;
        Customize::default()
    }
}

pub(crate) struct CustomizeCallbackDefault;
impl CustomizeCallback for CustomizeCallbackDefault {}

#[derive(Clone)]
pub(crate) struct CustomizeCallbackHolder(pub(crate) Rc<dyn CustomizeCallback>);

impl CustomizeCallbackHolder {
    pub(crate) fn new(callback: impl CustomizeCallback) -> CustomizeCallbackHolder {
        CustomizeCallbackHolder
    
    pub fn parse_from_parameter(parameter: &str) -> anyhow::Result<Customize> {
        fn parse_bool(v: &str) -> anyhow::Result<bool> {
            v.parse()
                .map_err(|_| CustomizeParseParameterError::CannotParseBool(v.to_owned()).into())
        }

        let mut r = Customize::default();
        for nv in parameter.split_whitespace() {
            let (n, v) = match nv.find('=') {
                Some(eq) => {
                    let n = &nv[..eq];
                    let v = &nv[eq + 1..];
                    (n, v)
                }
                None => (nv, "true"),
            };

            if n == "generate_accessors" {
                r.generate_accessors = Some(parse_bool(v)?);
            } else if n == "generate_getter" {
                r.generate_getter = Some(parse_bool(v)?);
            } else if n == "tokio_bytes" {
                r.tokio_bytes = Some(parse_bool(v)?);
            } else if n == "tokio_bytes_for_string" {
                r.tokio_bytes_for_string = Some(parse_bool(v)?);
            } else if n == "lite_runtime" {
                r.lite_runtime = Some(parse_bool(v)?);
            } else if n == "gen_mod_rs" {
                r.gen_mod_rs = Some(parse_bool(v)?);
            } else if n == "inside_protobuf" {
                r.inside_protobuf = Some(parse_bool(v)?);
            } else if n == "lite" {
                // Support Java and C++ protoc plugin syntax:
                // https://github.com/protocolbuffers/protobuf/issues/6489
                r.lite_runtime = Some(parse_bool(v)?);
            } else {
                return Err(CustomizeParseParameterError::UnknownOptionName(n.to_owned()).into());
            }
        }
        Ok(r)
    }