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```
```use crate::bounding_volume::AABB;
use crate::math::Isometry;
use crate::partitioning::BVHImpl;
use crate::query::{ContactPrediction, ContactPreprocessor};
use crate::shape::Shape;
use na::RealField;

/// Trait implemented by shapes composed of multiple simpler shapes.
///
/// A composite shape is composed of several shapes. Typically, it is a convex decomposition of
/// a concave shape.
pub trait CompositeShape<N: RealField> {
/// The number of sub-shape in this composide shape.
fn nparts(&self) -> usize;

/// Applies a transformation matrix and a function to each sub-shape of this concave
/// shape.
fn map_part_at(
&self,
_: usize,
m: &Isometry<N>,
_: &mut dyn FnMut(&Isometry<N>, &dyn Shape<N>),
);

/// Applies a transformation matrix and a function to each sub-shape of this concave
/// shape.
fn map_part_and_preprocessor_at(
&self,
_: usize,
m: &Isometry<N>,
prediction: &ContactPrediction<N>,
_: &mut dyn FnMut(&Isometry<N>, &dyn Shape<N>, &dyn ContactPreprocessor<N>),
);

// FIXME: the following two methods are not generic enough.
/// Gets the AABB of the shape identified by the index `i`.
fn aabb_at(&self, i: usize) -> AABB<N>;

/// Gets the acceleration structure of the concave shape.
fn bvh(&self) -> BVHImpl<N, usize, AABB<N>>;
}
```