@classmethod
def msdiff(cls, ms_start, ms_end=None):
    """
        Get difference in millis between current millis and provided millis.
        :param ms_start: Start millis
        :type ms_start: float
        :param ms_end: End millis (will use current if not provided)
        :type ms_end: float
        :return float
        :rtype float
        """
    if ms_end:
        return ms_end - ms_start
    else:
        return cls.mscurrent() - ms_start
