<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def synthesize(self, duration, freqs_in_hz=[440.]):
 """ Synthesize one or more sine waves Args: duration (numpy.timdelta64):
 The duration of the sound to be synthesized freqs_in_hz (list of float):
 Numbers representing the frequencies in hz that should be synthesized """

        freqs = np.array(freqs_in_hz)
        scaling = 1 / len(freqs)
        sr = int(self.samplerate)
        cps = freqs / sr
        ts = (duration / Seconds(1)) * sr
        ranges = np.array([np.arange(0, ts * c, c) for c in cps])
        raw = (np.sin(ranges * (2 * np.pi)) * scaling).sum(axis=0)
        return AudioSamples(raw, self.samplerate)