code: @Nullable
    public static CascadingStyleSheet readFromReader (@Nonnull final IHasReader aRP,
                                                      @Nonnull final ECSSVersion eVersion,
                                                      @Nullable final ICSSParseErrorHandler aCustomErrorHandler,
                                                      @Nullable final ICSSParseExceptionCallback aCustomExceptionHandler)
    {
      return readFromReader (aRP,
                             new CSSReaderSettings ().setCSSVersion (eVersion)
                                                     .setCustomErrorHandler (aCustomErrorHandler)
                                                     .setCustomExceptionHandler (aCustomExceptionHandler));
    }
docs: Read the CSS from the passed {@link IReaderProvider}. If the CSS contains
  an explicit <code>@charset</code> rule, it is ignored and the charset used
  to create the reader is used instead!
  
  @param aRP
  The reader provider to use. The reader is retrieved exactly once and
  closed anyway. May not be <code>null</code>.
  @param eVersion
  The CSS version to use. May not be <code>null</code>.
  @param aCustomErrorHandler
  An optional custom error handler that can be used to collect the
  recoverable parsing errors. May be <code>null</code>.
  @param aCustomExceptionHandler
  An optional custom exception handler that can be used to collect the
  unrecoverable parsing errors. May be <code>null</code>.
  @return <code>null</code> if reading failed, the CSS declarations
  otherwise.
  @since 3.7.3