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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 get_resource_listing(schema_dir, should_generate_resource_listing):
 """Return the resource listing document. :param schema_dir: the directory which contains swagger spec files :type schema_dir: string :param should_generate_resource_listing: when True a resource listing will be generated from the list of *.json files in the schema_dir. Otherwise return the contents of the resource listing file :type should_generate_resource_listing: boolean :returns: the contents of a resource listing document """

    listing_filename = os.path.join(schema_dir, API_DOCS_FILENAME)
    resource_listing = _load_resource_listing(listing_filename)

    if not should_generate_resource_listing:
        return resource_listing
    return generate_resource_listing(schema_dir, resource_listing)