def METHOD_NAME(self, t):
    """
    If 't' is an integer, returns the time at the specified index,
    together with the appropriate unit. Otherwise, if 't' is a float,
    returns the specified time with the appropriate unit.
    """
    if type(t) == int:
        return self.METHOD_NAME(t=self.t[t])
    unit = ['s', 'ms', r'\mu s', 'ns', 'ps']
    tval = t
    ui = 0
    if tval == 0: return tval, unit[ui]
    while tval < 1 and ui+1 < len(unit):
        tval *= 1e3
        ui += 1
    return tval, unit[ui]