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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def set_one_freq(self, f_ghz):
 """Set the code to calculate results at just one frequency. **Call signature** *f_ghz* The frequency to sample, in GHz. Returns *self* for convenience in chaining. """

        if not (f_ghz >= 0):
            raise ValueError('must have f_lo_ghz >= 0; got %r' % (f_lo_ghz,))

        self.in_vals[IN_VAL_NFREQ] = 1
        self.in_vals[IN_VAL_FREQ0] = f_ghz * 1e9 # GHz -> Hz
        self.in_vals[IN_VAL_LOGDFREQ] = 1.0
        return self