code: def _det_tc(detector_name, ra, dec, tc, ref_frame='geocentric'):
      
      if ref_frame == detector_name:
          return tc
      detector = Detector(detector_name)
      if ref_frame == 'geocentric':
          return tc + detector.time_delay_from_earth_center(ra, dec, tc)
      else:
          other = Detector(ref_frame)
          return tc + detector.time_delay_from_detector(other, ra, dec, tc)
docs: Returns the coalescence time of a signal in the given detector.
  
      Parameters
      ----------
      detector_name : string
          The name of the detector, e.g., 'H1'.
      ra : float
          The right ascension of the signal, in radians.
      dec : float
          The declination of the signal, in radians.
      tc : float
          The GPS time of the coalescence of the signal in the `ref_frame`.
      ref_frame : {'geocentric', string}
          The reference frame that the given coalescence time is defined in.
          May specify 'geocentric', or a detector name; default is 'geocentric'.
  
      Returns
      -------
      float :
          The GPS time of the coalescence in detector `detector_name`.