Function prelu_backward 

pub fn prelu_backward<T: Triton, const BLOCK_SIZE: i32>(
    dy_ptr: T::Pointer<f32>,
    x_ptr: T::Pointer<f32>,
    slope_ptr: T::Pointer<f32>,
    dx_ptr: T::Pointer<f32>,
    dslope_ptr: T::Pointer<f32>,
    n_elements: i32,
)
where
    T::I32Tensor: Tensor<i32, 1> + Comparison<i32, BoolTensor = T::BoolTensor>,
    T::Pointer<f32>: AddOffsets<i32, 1, T::I32Tensor, Output = T::Tensor<T::Pointer<f32>>>,

Backward: dx = dy if x >= 0 else slope * dy; dslope = dy * min(x, 0) = dy * x if x < 0 else 0