Interpolate a value from start to end at a given progress.

        :param start: The start value.
        :param end: The end value.
        :param step: The current step.
        :param total_steps: The total number of steps.
        :return: The interpolated value at the given progress.

def _interpolate(start, end, step, total_steps):
        """
        Interpolate a value from start to end at a given progress.

        :param start: The start value.
        :param end: The end value.
        :param step: The current step.
        :param total_steps: The total number of steps.
        :return: The interpolated value at the given progress.
        """
        diff = end - start
        progress = step / (total_steps - 1)
        return start + progress * diff