code: public static boolean isValidCSS (@Nonnull final IReadableResource aRes,
                                      @Nonnull final Charset aFallbackCharset,
                                      @Nonnull final ECSSVersion eVersion)
    {
      ValueEnforcer.notNull (aRes, "Resource");
      ValueEnforcer.notNull (aFallbackCharset, "FallbackCharset");
      ValueEnforcer.notNull (eVersion, "Version");
  
      final Reader aReader = aRes.getReader (aFallbackCharset);
      if (aReader == null)
      {
        LOGGER.warn ("Failed to open CSS reader " + aRes);
        return false;
      }
      return isValidCSS (aReader, eVersion);
    }
docs: Check if the passed CSS resource can be parsed without error
  
  @param aRes
  The resource to be parsed. May not be <code>null</code>.
  @param aFallbackCharset
  The charset to be used for reading the CSS file in case neither a
  <code>@charset</code> rule nor a BOM is present. May not be
  <code>null</code>.
  @param eVersion
  The CSS version to be used for scanning. May not be
  <code>null</code>.
  @return <code>true</code> if the file can be parsed without error,
  <code>false</code> if not