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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 ToInternal(self):
 """Convert wavelengths to the internal representation of angstroms. For internal use only."""

        self.validate_units()
        savewunits = self.waveunits
        angwave = self.waveunits.Convert(self._wavetable, 'angstrom')
        self._wavetable = angwave.copy()
        self.waveunits = savewunits