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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 dcs_modules():
 """Get names of DCS modules, depending on execution environment. If being packaged with PyInstaller, modules aren't discoverable dynamically by scanning source directory because `FrozenImporter` doesn't implement `iter_modules` method. But it is still possible to find all potential DCS modules by iterating through `toc`, which contains list of all "frozen" resources."""


    dcs_dirname = os.path.dirname(__file__)
    module_prefix = __package__ + '.'

    if getattr(sys, 'frozen', False):
        importer = pkgutil.get_importer(dcs_dirname)
        return [module for module in list(importer.toc) if module.startswith(module_prefix) and module.count('.') == 2]
    else:
        return [module_prefix + name for _, name, is_pkg in pkgutil.iter_modules([dcs_dirname]) if not is_pkg]