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use crate::{KernelError, PositiveDefiniteKernel, Value};

pub trait ValueDifferentiableKernel<T>: PositiveDefiniteKernel<T>
where
    T: Value,
{
    fn ln_diff_value(
        &self,
        params: &[f64],
        x: &Vec<f64>,
        xprime: &Vec<f64>,
    ) -> Result<Vec<f64>, KernelError>;
}