'Set the table masked property.
Parameters
masked : bool
State of table masking (`True` or `False`)'

def _set_masked(self, masked):

    if hasattr(self, u'_masked'):
        if ((self._masked is None) and (masked in [False, True])):
            self._masked = masked
        elif ((self._masked is False) and (masked is True)):
            log.info(u'Upgrading    Table    to    masked    Table.    Use    Table.filled()    to    convert    to    unmasked    table.')
            self._masked = masked
        elif (self._masked is masked):
            raise Exception(u'Masked    attribute    is    already    set    to    {0}'.format(masked))
        else:
            raise Exception(u'Cannot    change    masked    attribute    to    {0}    once    it    is    set    to    {1}'.format(masked, self._masked))
    elif (masked in [True, False, None]):
        self._masked = masked
    else:
        raise ValueError(u'masked    should    be    one    of    True,    False,    None')
    if self._masked:
        self._column_class = self.MaskedColumn
    else:
        self._column_class = self.Column
