Request histogram data.

        This method is blocking.

        https://interactivebrokers.github.io/tws-api/histograms.html

        Args:
            contract: Contract to query.
            useRTH: If True then only show data from within Regular
                Trading Hours, if False then show all data.
            period: Period of which data is being requested, for example
                '3 days'.

def reqHistogramData(
            self, contract: Contract,
            useRTH: bool, period: str) -> List[HistogramData]:
        """
        Request histogram data.

        This method is blocking.

        https://interactivebrokers.github.io/tws-api/histograms.html

        Args:
            contract: Contract to query.
            useRTH: If True then only show data from within Regular
                Trading Hours, if False then show all data.
            period: Period of which data is being requested, for example
                '3 days'.
        """
        return self._run(
            self.reqHistogramDataAsync(contract, useRTH, period))