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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 get_subgraphs_as_molecules(self, use_weights=False):
 """ Retrieve subgraphs as molecules, useful for extracting molecules from periodic crystals. Will only return unique molecules, not any duplicates present in the crystal (a duplicate defined as an isomorphic subgraph). :param use_weights (bool):
 If True, only treat subgraphs as isomorphic if edges have the same weights. Typically, this means molecules will need to have the same bond lengths to be defined as duplicates, otherwise bond lengths can differ. This is a fairly robust approach, but will treat e.g. enantiomers as being duplicates. :return: list of unique Molecules in Structure """


        # creating a supercell is an easy way to extract
        # molecules (and not, e.g., layers of a 2D crystal)
        # without adding extra logic
        if getattr(self, '_supercell_sg', None) is None:
            self._supercell_sg = supercell_sg = self*(3,3,3)

        # make undirected to find connected subgraphs
        supercell_sg.graph = nx.Graph(supercell_sg.graph)

        # find subgraphs
        all_subgraphs = list(nx.connected_component_subgraphs(supercell_sg.graph))

        # discount subgraphs that lie across *supercell* boundaries
        # these will subgraphs representing crystals
        molecule_subgraphs = []
        for subgraph in all_subgraphs:
            intersects_boundary = any([d['to_jimage'] != (0, 0, 0)
                                      for u, v, d in subgraph.edges(data=True)])
            if not intersects_boundary:
                molecule_subgraphs.append(subgraph)

        # add specie names to graph to be able to test for isomorphism
        for subgraph in molecule_subgraphs:
            for n in subgraph:
                subgraph.add_node(n, specie=str(supercell_sg.structure[n].specie))

        # now define how we test for isomorphism
        def node_match(n1, n2):
            return n1['specie'] == n2['specie']
        def edge_match(e1, e2):
            if use_weights:
                return e1['weight'] == e2['weight']
            else:
                return True

        # prune duplicate subgraphs
        unique_subgraphs = []
        for subgraph in molecule_subgraphs:

            already_present = [nx.is_isomorphic(subgraph, g,
                                                node_match=node_match,
                                                edge_match=edge_match)
                               for g in unique_subgraphs]

            if not any(already_present):
                unique_subgraphs.append(subgraph)

        # get Molecule objects for each subgraph
        molecules = []
        for subgraph in unique_subgraphs:

            coords = [supercell_sg.structure[n].coords for n
                      in subgraph.nodes()]
            species = [supercell_sg.structure[n].specie for n
                      in subgraph.nodes()]

            molecule = Molecule(species, coords)

            # shift so origin is at center of mass
            molecule = molecule.get_centered_molecule()

            molecules.append(molecule)

        return molecules