'Return a human-readable string representation for this ``AlignedSent``.
:rtype: str'

def __str__(self):

    source = (u'    '.join(self._words)[:20] + u'...')
    target = (u'    '.join(self._mots)[:20] + u'...')
    return (u"<AlignedSent:    '%s'    ->    '%s'>" % (source, target))
