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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 _convert(cls, record):
 """ Core method of the converter. Converts a single dictionary into another dictionary. """

        if not record:
            return {}

        converted_dict = {}
        for field in cls.conversion:
            key = field[0]
            if len(field) >= 2 and field[1]:
                converted_key = field[1]
            else:
                converted_key = key
            if len(field) >= 3 and field[2]:
                conversion_method = field[2]
            else:
                conversion_method = cls.default_conversion_method
            if len(field) >= 4:
                converter = field[3]
            else:
                converter = None
            try:
                value = conversion_method(record[key])
            except KeyError:
                continue
            if converter:
                value = converter._convert_internal(value)
            if converted_key is APPEND:
                if isinstance(value, list):
                    for v in value:
                        converted_dict.update(v)
                else:
                    converted_dict.update(value)
            else:
                converted_dict[converted_key] = value
        return converted_dict