docs: private static @CheckForNull VersionNumber toVersion(@CheckForNull String versionString) {
          if (versionString == null) {
              return null;
          }
  
          try {
              return new VersionNumber(versionString);
          } catch (NumberFormatException e) {
              try {
                  // for non-released version of Jenkins, this looks like "1.345 (private-foobar), so try to approximate.
                  int idx = versionString.indexOf(' ');
                  if (idx > 0) {
                      return new VersionNumber(versionString.substring(0,idx));
                  }
              } catch (NumberFormatException ignored) {
                  // fall through
              }
  
              // totally unparseable
              return null;
          } catch (IllegalArgumentException e) {
              // totally unparseable
              return null;
          }
      }