Perform http request to get translation from given surah, ayah and
        language.

        Parameter:
            :surah      --  Surah index from API pages.
            :ayat       --  Ayat key.
            :lang       --  Language code.

        Return:
            :string     --  Translation from given surah and ayat.

def __get_translation(self, surah, ayah, lang):
        """
        Perform http request to get translation from given surah, ayah and
        language.

        Parameter:
            :surah      --  Surah index from API pages.
            :ayat       --  Ayat key.
            :lang       --  Language code.

        Return:
            :string     --  Translation from given surah and ayat.
        """
        # Construct url to fetch translation data.
        url = '{base}/translations/{lang}/{lang}_translation_{surah}.json'.format(
            base=self.BASE_API, lang=lang, surah=int(surah)
        )
        try:
            response = urlopen(url)                             # Fetch data from give url.
            data = json.loads(response.read().decode('utf-8'))  # Get response and convert to dict.
            translation = data['verse'][ayah]
        except ODOAException:
            return None
        else:
            return translation