Checks to see if the inputed tag is valid or not.
        
        :param      tag | <str>
        
        :return     <bool>

def isTagValid( self, tag ):
        """
        Checks to see if the inputed tag is valid or not.
        
        :param      tag | <str>
        
        :return     <bool>
        """
        if ( self._options is not None and \
             not nativestring(tag) in self._options \
             and not self.isInsertAllowed() ):
            return False
        
        elif ( self.isUnique() and self.hasTag(tag) ):
            return False
        
        return True