def get_treetagger_triple(string):
    """ 
    Split a single line from TreeTagger's output to obtain a
    (word,pos,lemma) triple.
    """ 

    elems = string.split('\t') 
    # Lines that don't contain exactly 2 tabs are ignored.  These are
    # usually lines containing a single <repdns> or <repurl> element
    # which TreeTagger uses to indicate that it has replaced the token
    # in the previous (token, pos, lemma) triple with a special symbol
    # (e.g. dns-remplacé). The replaced text is in the "text"
    # attribute of the repdns or repurl element.
    if len(elems) == 3:
        return elems
    else:
        return None