Returns the name of the column at the inputed index.
        
        :param      index | <int>
        
        :return     <str>

def columnNameAt( self, index ):
        """
        Returns the name of the column at the inputed index.
        
        :param      index | <int>
        
        :return     <str>
        """
        columns = self.columns()
        if ( 0 <= index and index < len(columns) ):
            return columns[index]
        return ''