'Takes a collection of defns and returns the unique list of defns.'

@classmethod
def unique_definitions(cls, defns):

    unique_defns = []
    for defn in defns:
        for unique_defn in unique_defns:
            if ((unique_defn.path == defn.path) and (unique_defn == defn)):
                break
        else:
            unique_defns.append(defn)
    return unique_defns
