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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 modules(self):
 """Iterates over the defined Modules."""

        defmodule = lib.EnvGetNextDefmodule(self._env, ffi.NULL)

        while defmodule != ffi.NULL:
            yield Module(self._env, defmodule)

            defmodule = lib.EnvGetNextDefmodule(self._env, defmodule)