code: def phase2radians(phasedata, v0):
      
      fi = [2*np.pi*v0*xx for xx in phasedata]
      return fi
docs: Convert phase in seconds to phase in radians
  
      Parameters
      ----------
      phasedata: np.array
          Data array of phase in seconds
      v0: float
          Nominal oscillator frequency in Hz
  
      Returns
      -------
      fi:
          phase data in radians