Function extract_pypi_min_version 

pub fn extract_pypi_min_version(version_req: &str) -> Option<String>

Extract the minimum version number from a PEP 440 version specifier.

Examples

assert_eq!(extract_pypi_min_version(">=8.0"), Some("8.0".to_string()));
assert_eq!(extract_pypi_min_version(">=1.0,<2.0"), Some("1.0".to_string()));
assert_eq!(extract_pypi_min_version("~=1.4.2"), Some("1.4.2".to_string()));
assert_eq!(extract_pypi_min_version("==2.0.0"), Some("2.0.0".to_string()));