Function is_prerelease 

pub fn is_prerelease(version: &str) -> bool

Detects whether a NuGet version string is a prerelease version.

NuGet’s rule is structural, not keyword-based: any version with a - suffix after the numeric core is a prerelease, regardless of the label used. This must not be confused with deps_core::registry::Version’s defaulted keyword-sniff implementation, which recognizes only -alpha|-beta|-rc|-dev|-pre|-snapshot|-canary|-nightly — standard .NET labels like -rtm, -servicing.23, -CI-*, and -final all match none of those keywords and would be misreported as stable. See the NuGetVersion hand-written Version impl in types.rs, which delegates here instead of using impl_version!.