def METHOD_NAME(ifos):
    """
    Calculate the area in which signal time differences are physically allowed
    Parameters
    ----------
    ifos: list of strings
        list of interferometers
    Returns
    -------
    allowed_area: float
        area in units of seconds^(n_ifos-1) that coincident signals will occupy
    """
    n_ifos = len(ifos)
    if n_ifos == 2:
        det0 = pycbc.detector.Detector(ifos[0])
        det1 = pycbc.detector.Detector(ifos[1])
        allowed_area = 2 * det0.light_travel_time_to_detector(det1)
    elif n_ifos == 3:
        dets = {}
        tofs = numpy.zeros(n_ifos)
        ifo2_num = []
        # set up detector objects
        for ifo in ifos:
            dets[ifo] = pycbc.detector.Detector(ifo)
        # calculate travel time between detectors
        for i, ifo in enumerate(ifos):
            ifo2_num.append(int(numpy.mod(i + 1, n_ifos)))
            det0 = dets[ifo]
            det1 = dets[ifos[ifo2_num[i]]]
            tofs[i] = det0.light_travel_time_to_detector(det1)
        # calculate allowed area
        phi_12 = numpy.arccos((tofs[0]**2 + tofs[1]**2 - tofs[2]**2)
                              / (2 * tofs[0] * tofs[1]))
        allowed_area = numpy.pi * tofs[0] * tofs[1] * numpy.sin(phi_12)
    else:
        raise NotImplementedError("Not able to deal with more than 3 ifos")
    return allowed_area