Ensure the Fold block is valid.

def validate(self):
        """Ensure the Fold block is valid."""
        if not isinstance(self.fold_scope_location, FoldScopeLocation):
            raise TypeError(u'Expected a FoldScopeLocation for fold_scope_location, got: {} '
                            u'{}'.format(type(self.fold_scope_location), self.fold_scope_location))