              Data items in the STRUCT_SHEET_TOPOLOGY category record details\
               about the topology of the residue ranges that form a beta sheet.\
               All topology linkages are pairwise, and the specified pairs are\
               assumed to be successive in the amino acid sequence. These\
               data items are useful in describing various simple and complex\
               folds, but they become inadequate when the strands in the sheet\
               come from more than one chain. One can alternatively use the\
               STRUCT_SHEET_ORDER data items to describe both single and\
               multiple chain-containing sheets.