Function chi_angles_atoms 

pub fn chi_angles_atoms(
    res3: &str,
) -> &'static [(&'static str, &'static str, &'static str, &'static str)]

Sidechain chi-angle atom tuples for a residue given by 3-letter code.

Returns a slice of (a1, a2, a3, a4) tuples, one per chi angle (chi1 first). An empty slice means the residue has no rotatable sidechains.

Source: OpenFold / AlphaFold2 residue_constants.py.