Initialize a DocumentAnalysis object from a json dictionary.

def _from_dict(cls, _dict):
        """Initialize a DocumentAnalysis object from a json dictionary."""
        args = {}
        if 'tones' in _dict:
            args['tones'] = [
                ToneScore._from_dict(x) for x in (_dict.get('tones'))
            ]
        if 'tone_categories' in _dict:
            args['tone_categories'] = [
                ToneCategory._from_dict(x)
                for x in (_dict.get('tone_categories'))
            ]
        if 'warning' in _dict:
            args['warning'] = _dict.get('warning')
        return cls(**args)