code: public PackageInfo getPackageInfo(final String packageName) {
          if (closed.get()) {
              throw new IllegalArgumentException("Cannot use a ScanResult after it has been closed");
          }
          if (!scanSpec.enableClassInfo) {
              throw new IllegalArgumentException("Please call ClassGraph#enableClassInfo() before #scan()");
          }
          return packageNameToPackageInfo.get(packageName);
      }
docs: Get the {@link PackageInfo} object for the named package, or null if no package of the requested name was
  found during the scan.
  
  @param packageName
  The package name.
  @return The {@link PackageInfo} object for the named package, or null if the package was not found.