Generalized setter for boolean properties on the ``<a:tblPr>`` child
        element, setting *propname* attribute appropriately based on *value*.
        If *value* is True, the attribute is set to "1"; a tblPr child
        element is added if necessary. If *value* is False, the *propname*
        attribute is removed if present, allowing its default value of False
        to be its effective value.

def _set_boolean_property(self, propname, value):
        """
        Generalized setter for boolean properties on the ``<a:tblPr>`` child
        element, setting *propname* attribute appropriately based on *value*.
        If *value* is True, the attribute is set to "1"; a tblPr child
        element is added if necessary. If *value* is False, the *propname*
        attribute is removed if present, allowing its default value of False
        to be its effective value.
        """
        if value not in (True, False):
            raise ValueError(
                "assigned value must be either True or False, got %s" %
                value
            )
        tblPr = self.get_or_add_tblPr()
        setattr(tblPr, propname, value)