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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_format_modules(lang):
 """ Does the heavy lifting of finding format modules. """

    if check_for_language(lang):
        format_locations = []
        for path in CUSTOM_FORMAT_MODULE_PATHS:
            format_locations.append(path + '.%s')
        format_locations.append('django.conf.locale.%s')
        locale = to_locale(lang)
        locales = [locale]
        if '_' in locale:
            locales.append(locale.split('_')[0])
        for location in format_locations:
            for loc in locales:
                try:
                    yield import_module('.formats', location % loc)
                except ImportError:
                    pass