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: lib.rs
    path of file: ./repos/conrod/backends/conrod_example_shared/src
    
    the code of the file until where you have to start completion: //! This crate is used for sharing a few items between the conrod examples.
//!
//! The module contains:
//!
//! - `pub struct DemoApp` as a demonstration of some state we want to change.
//! - `pub fn gui` as a demonstration of all widgets, some of which mutate our `DemoApp`.
//! - `pub struct Ids` - a set of all `widget::Id`s used in the `gui` fn.
//!
//! By sharing these items between
    
pub fn theme() -> conrod_core::Theme {
    use conrod_core::position::{Align, Direction, Padding, Position, Relative};
    conrod_core::Theme {
        name: "Demo Theme".to_string(),
        padding: Padding::none(),
        x_position: Position::Relative(Relative::Align(Align::Start), None),
        y_position: Position::Relative(Relative::Direction(Direction::Backwards, 20.0), None),
        background_color: conrod_core::color::DARK_CHARCOAL,
        shape_color: conrod_core::color::LIGHT_CHARCOAL,
        border_color: conrod_core::color::BLACK,
        border_width: 0.0,
        label_color: conrod_core::color::WHITE,
        font_id: None,
        font_size_large: 26,
        font_size_medium: 18,
        font_size_small: 12,
        widget_styling: conrod_core::theme::StyleMap::default(),
        mouse_drag_threshold: 0.0,
        double_click_threshold: std::time::Duration::from_millis(500),
    }
}