Returns the index of the column at the given name.
        
        :param      name | <str>
        
        :return     <int> (-1 if not found)

def column( self, name ):
        """
        Returns the index of the column at the given name.
        
        :param      name | <str>
        
        :return     <int> (-1 if not found)
        """
        columns = self.columns()
        if ( name in columns ):
            return columns.index(name)
        return -1