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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 classes(self):
 """Iterate over the defined Classes."""

        defclass = lib.EnvGetNextDefclass(self._env, ffi.NULL)

        while defclass != ffi.NULL:
            yield Class(self._env, defclass)

            defclass = lib.EnvGetNextDefclass(self._env, defclass)