Returns a list of the API URLs.

def _init_request_urls(self, api_urls):
        """
        Returns a list of the API URLs.
        """
        if not isinstance(api_urls, (str, list, tuple)):
            raise TypeError('api_urls needs to be string or iterable!')

        if isinstance(api_urls, str):
            api_urls = (api_urls,)

        api_urls = list(api_urls)

        for url in api_urls:
            if not url.startswith('http://') and \
               not url.startswith('https://'):
                raise ValueError(('URL "%s" contains an invalid or missing'
                                 ' scheme' % (url)))

        return list(api_urls)