code: public static boolean isValidCSS (@Nonnull @WillClose final InputStream aIS,
                                      @Nonnull final Charset aFallbackCharset,
                                      @Nonnull final ECSSVersion eVersion)
    {
      ValueEnforcer.notNull (aIS, "InputStream");
      ValueEnforcer.notNull (aFallbackCharset, "FallbackCharset");
  
      return isValidCSS (StreamHelper.createReader (aIS, aFallbackCharset), eVersion);
    }
docs: Check if the passed input stream can be resembled to valid CSS content.
  This is accomplished by fully parsing the CSS file each time the method is
  called. This is similar to calling
  {@link #readFromStream(IHasInputStream,Charset, ECSSVersion)} and checking
  for a non-<code>null</code> result.
  
  @param aIS
  The input stream to use. Is automatically closed. May not be
  <code>null</code>.
  @param aFallbackCharset
  The charset to be used 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 use. May not be <code>null</code>.
  @return <code>true</code> if the CSS is valid according to the version,
  <code>false</code> if not