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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 _iter_module_files():
 """This iterates over all relevant Python files. It goes through all loaded files from modules, all files in folders of already loaded modules as well as all files reachable through a package. """

    # The list call is necessary on Python 3 in case the module
    # dictionary modifies during iteration.
    for module in list(sys.modules.values()):
        if module is None:
            continue
        filename = getattr(module, "__file__", None)
        if filename:
            if os.path.isdir(filename) and os.path.exists(
                os.path.join(filename, "__init__.py")
            ):
                filename = os.path.join(filename, "__init__.py")

            old = None
            while not os.path.isfile(filename):
                old = filename
                filename = os.path.dirname(filename)
                if filename == old:
                    break
            else:
                if filename[-4:] in (".pyc", ".pyo"):
                    filename = filename[:-1]
                yield filename