def short_title(self, key, value):
    """Populate the ``short_title`` key.

    Also populates the ``title_variants`` key through side effects.
    """
    short_title = value.get('a')
    title_variants = self.get('title_variants', [])

    if value.get('u'):
        short_title = value.get('u')
        title_variants.append(value.get('a'))

    self['title_variants'] = title_variants
    return short_title
Populate the ``short_title`` key.

    Also populates the ``title_variants`` key through side effects.