Function standard_base_pair_geometry 

pub fn standard_base_pair_geometry(
    structure: &Structure,
    geometry: WatsonCrickGeometry,
    maximum_contact_distance: f32,
) -> Result<Vec<GeometricBasePair>, SpatialError>

Finds standard A–T/U and G–C pairs without a component dictionary.

Requires positioned C1’, C2, C4 and C6 atoms, reference-plane agreement, and at least two complementary edge contacts. Unknown or modified component names are skipped; dictionary-backed chemistry is available through the molframe::analysis domain. Positions are read from the first model.

Errors

Returns a spatial error for non-finite or non-positive distance limits.