'A chunk of chunks that make up a prepositional noun phrase (i.e., PP + NP).
When the output of the parser includes PP-attachment,
PNPChunck.anchor will yield the chunk that is clarified by the preposition.
For example: "the cat went [for the mouse] [with its claws]":
- [went] what? => for the mouse,
- [went] how? => with its claws.'

def __init__(self, *args, **kwargs):

    self.anchor = None
    self.chunks = []
    Chunk.__init__(self, *args, **kwargs)
