<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def constraints(self, chunk):
 """ Returns a list of constraints that match the given Chunk. """

        a = [self._map1[w.index] for w in chunk.words if w.index in self._map1]
        b = []; [b.append(constraint) for constraint in a if constraint not in b]
        return b