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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 authenticate_external(self, auth_params):
 """Verify credentials using the external auth library. in auth_params of type str The auth parameters, credentials, etc. out result of type str The authentification result. """

        if not isinstance(auth_params, list):
            raise TypeError("auth_params can only be an instance of type list")
        for a in auth_params[:10]:
            if not isinstance(a, basestring):
                raise TypeError(
                        "array can only contain objects of type basestring")
        result = self._call("authenticateExternal",
                     in_p=[auth_params])
        return result