@classmethod
def getUnitBySymbol(cls, symbol):
    """Return the unit with symbol `symbol`.

        Args:
            symbol (str): symbol to look-up

        Returns:
            :class:`Unit` sub-class, if a unit with given `symbol` exists
                within the :class:`Unit` sub-class associated with this
                :class:`Quantity` sub-class, otherwise None
        """
    return cls.Unit.getUnitBySymbol(symbol)
