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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 compute_rotsym(self, threshold=1e-3*angstrom):
 """Compute the rotational symmetry number. Optional argument: | ``threshold`` -- only when a rotation results in an rmsd below the given threshold, the rotation is considered to transform the molecule onto itself. """

        # Generate a graph with a more permissive threshold for bond lengths:
        # (is convenient in case of transition state geometries)
        graph = MolecularGraph.from_geometry(self, scaling=1.5)
        try:
            return compute_rotsym(self, graph, threshold)
        except ValueError:
            raise ValueError("The rotational symmetry number can only be computed when the graph is fully connected.")