def compute_rotsym(molecule, graph, threshold=<NUM_LIT>*angstrom):
result = <NUM_LIT:0><EOL>for match in graph.symmetries:<EOL><INDENT>permutation = list(j for i,j in sorted(match.forward.items()))<EOL>new_coordinates = molecule.coordinates[permutation]<EOL>rmsd = fit_rmsd(molecule.coordinates, new_coordinates)[<NUM_LIT:2>]<EOL>if rmsd < threshold:<EOL><INDENT>result += <NUM_LIT:1><EOL><DEDENT><DEDENT>return result<EOL>
Compute the rotational symmetry number

       Arguments:
        | ``molecule``  --  The molecule
        | ``graph``  --  The corresponding bond graph

       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.