secstruct: Secondary structure, e.g. "EEEELLEEEE". If undefined, sec struct will be chosen based on the value of the 'use_dssp' option
sheet_topology: String describing sheet topology, of the format A-B.P.R, where A is the strand number of the first strand in primary space, B is the strand number of the second strand in primary space, P is 'P' for parallel and 'A' for antiparallel, and R is the register shift. E.g. "1-2.A.-1".
use_dssp: Use dssp to aito-detect secondary structure.