See if this ticker has a valid bid and ask.

def hasBidAsk(self) -> bool:
        """
        See if this ticker has a valid bid and ask.
        """
        return (
            self.bid != -1 and not isNan(self.bid) and self.bidSize > 0 and
            self.ask != -1 and not isNan(self.ask) and self.askSize > 0)