code: function residualForm (token) {
  
      var tokenString = token.string;
  
      if (token.hasSuffix('gue') || token.hasSuffix('gué') || token.hasSuffix('guê')) {
        token.replaceSuffixInRegion(['ue', 'ué', 'uê'], '', 'rv');
      }
  
      if (token.hasSuffix('cie') || token.hasSuffix('cié') || token.hasSuffix('ciê')) {
        token.replaceSuffixInRegion(['ie', 'ié', 'iê'], '', 'rv');
      }
  
      if (tokenString === token.string) {
        token.replaceSuffixInRegion(['e', 'é', 'ê'], '', 'rv');
      }
  
      token.replaceSuffixInRegion('ç', 'c', 'all');
  
      return token;
    }
docs: Step 5: Residual form.
  
  This step should always be performed.
  
  @param  {Token} token Token to stem.
  @return {Token}       Stemmed token.