'Returns the default transcript language for this video module.
Args:
transcripts (dict): A dict with all transcripts and a sub.'

def get_default_transcript_language(self, transcripts):

    (sub, other_lang) = (transcripts['sub'], transcripts['transcripts'])
    if (self.transcript_language in other_lang):
        transcript_language = self.transcript_language
    elif sub:
        transcript_language = u'en'
    elif (len(other_lang) > 0):
        transcript_language = sorted(other_lang)[0]
    else:
        transcript_language = u'en'
    return transcript_language
