code: def extractValue(self, model, item):
          
          certPath = super(CertificateColumn, self).extractValue(model, item)
          return certPath.path.decode('utf-8', 'replace')
docs: Get the path referenced by this column's attribute.
  
          @param model: Either a TabularDataModel or a ScrollableView, depending
          on what this column is part of.
  
          @param item: A port item instance (as defined by L{xmantissa.port}).
  
          @rtype: C{unicode}