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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def site_specific_nn_occupation( self ):
 """ Returns the number of occupied nearest neighbour sites, classified by site type. Args: None Returns: (Dict(Str:Int)):
 Dictionary of nearest-neighbour occupied site numbers, classified by site label, e.g. { 'A' : 2, 'B' : 1 }. """

        to_return = { l : 0 for l in set( ( site.label for site in self.p_neighbours ) ) }
        for site in self.p_neighbours:
            if site.is_occupied:
             to_return[ site.label ] += 1
        return to_return