Function parse_license_expression 

pub fn parse_license_expression(license: &str) -> BTreeSet<String>

extracts individual license IDs from an SPDX expression.

parses the expression and returns all license IDs found, including LicenseRef- identifiers. if parsing fails, returns the original string as a single-element set.

Example

use sbom_model::parse_license_expression;

let ids = parse_license_expression("MIT OR Apache-2.0");
assert!(ids.contains("MIT"));
assert!(ids.contains("Apache-2.0"));

let ids = parse_license_expression("LicenseRef-proprietary AND Apache-2.0");
assert!(ids.contains("LicenseRef-proprietary"));
assert!(ids.contains("Apache-2.0"));