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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 _def_check(self):
 """ Checks that the definition provided contains only valid arguments for a text index. """

        if self._def != dict():
            for key, val in iteritems_(self._def):
                if key not in list(TEXT_INDEX_ARGS.keys()):
                    raise CloudantArgumentError(127, key)
                if not isinstance(val, TEXT_INDEX_ARGS[key]):
                    raise CloudantArgumentError(128, key, TEXT_INDEX_ARGS[key])