Add a new variable to the configuration.

        name - Complete name of the variable in the form group.name
        fetch_as - String representation of the type the variable should be
                   fetched as (i.e uint8_t, float, FP16, etc)

        If no fetch_as type is supplied, then the stored as type will be used
        (i.e the type of the fetched variable is the same as it's stored in the
        Crazyflie).

def add_variable(self, name, fetch_as=None):
        """Add a new variable to the configuration.

        name - Complete name of the variable in the form group.name
        fetch_as - String representation of the type the variable should be
                   fetched as (i.e uint8_t, float, FP16, etc)

        If no fetch_as type is supplied, then the stored as type will be used
        (i.e the type of the fetched variable is the same as it's stored in the
        Crazyflie)."""
        if fetch_as:
            self.variables.append(LogVariable(name, fetch_as))
        else:
            # We cannot determine the default type until we have connected. So
            # save the name and we will add these once we are connected.
            self.default_fetch_as.append(name)