[modeller_usage] clustering

Hi,

I wondered if somebody could help me. Is it at all possible to cluster existing pdb files ? If so can you tell me how to arrange the input arguments I tried using

a=automodel env, alnfile = '', knowns = ('pdb1', 'pdb2'... with cluster(cluster_cut).

Any help/example scripts would be very much appreciated

Thanks

Miriam Leach