Return column index whose name is :param:`column`

        :raises: `ValueError` when no column with :param:`colname` found

def colindex_by_colname(self, colname):
        """Return column index whose name is :param:`column`

        :raises: `ValueError` when no column with :param:`colname` found
        """
        for i, coldef in enumerate(self):    # iterate each column's definition
            if coldef.name == colname:
                return i
        raise ValueError('No column named "%s" found' % (colname))