This is the code:
```rust
    pub fn process_sample(&mut self, sample: &StereoSample) -> StereoSample {
        let in_state_2 = self.in_states[1].clone();
        self.in_states[1] = self.in_states[0].clone();
        self.in_states[0] = sample.clone();

        let out_state_2 = self.out_states[1].clone();
        self.out_states[1] = self.out_states[0].clone();

        let new_sample = StereoSample {
            left: self.coeffs.a0_div_b0 * sample.left
                + self.coeffs.a1_div_b0 * self.in_states[1].left
                + self.coeffs.a2_div_b0 * in_state_2.left
                + self.coeffs.b1_div_b0 * self.out_states[1].left
                + self.coeffs.b2_div_b0 * out_state_2.left,
            right: self.coeffs.a0_div_b0 * sample.right
                + self.coeffs.a1_div_b0 * self.in_states[1].right
                + self.coeffs.a2_div_b0 * in_state_2.right
                + self.coeffs.b1_div_b0 * self.out_states[1].right
                + self.coeffs.b2_div_b0 * out_state_2.right,
        };

        self.out_states[0] = new_sample.clone();

        new_sample
    }
```