'Make sure that all Column objects have correct class for this type of
Table.  For a base Table this most commonly means setting to
MaskedColumn if the table is masked.  Table subclasses like QTable
override this method.'

def _convert_col_for_table(self, col):

    if ((col.__class__ is not self.ColumnClass) and isinstance(col, Column)):
        col = self.ColumnClass(col)
    return col
