Selects VoltagePairs within a certain voltage range.

        Args:
            min_voltage (float): The minimum allowable voltage for a given
                step.
            max_voltage (float): The maximum allowable voltage allowable for a
                given step.

        Returns:
            A list of VoltagePair objects

def _select_in_voltage_range(self, min_voltage=None, max_voltage=None):
        """
        Selects VoltagePairs within a certain voltage range.

        Args:
            min_voltage (float): The minimum allowable voltage for a given
                step.
            max_voltage (float): The maximum allowable voltage allowable for a
                given step.

        Returns:
            A list of VoltagePair objects
        """
        min_voltage = min_voltage if min_voltage is not None \
            else self.min_voltage
        max_voltage = max_voltage if max_voltage is not None \
            else self.max_voltage
        return list(filter(lambda p: min_voltage <= p.voltage <= max_voltage,
                           self.voltage_pairs))