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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 _find_parameter(cls, dct):
        '''Search for the 'key=True' case, and confirm no more than one parameter has that property.'''

        num_found = 0
        field = None

        for key, val in dct.iteritems():
            if isinstance(val, DataType) and val.is_key:
                field = key
                num_found += 1

        if num_found > 1:
            raise SetupError(502)
        elif num_found == 0:
            return False

        dct['_cbs_key_field'] = field
        dct['key'] = cls._build_prop(field)
        return True