//! Caller- or molframe-supplied secondary-structure state.
/// Reversible per-residue cartoon classification. The renderer never infers
/// this state; callers may apply records produced by `molframe`.
#[derive(Clone, Copy, PartialEq, Eq, Debug, Default)]
pub enum SecondaryStructure {
/// Missing or not yet evaluated assignment.
#[default]
Unknown,
/// No helix or sheet assignment.
Coil,
/// Alpha helix.
Helix,
/// Beta strand.
Strand,
/// Hydrogen-bonded turn.
Turn,
}