If given a blueprint, SecondaryStructureFilter now scans the strand pairing and determines whether it is possible for all "E" residues to be paired. For these residues, DSSP will always return "L" because there is no hydrogen bonding. The wanted ss string is modified by converting unpaired residues to "h" (which means L or E). This does not change the behavior if a ss string is specified, or if a complete blueprint with 100% paired strands is specified. This change allows checking the secondary structure of partially-built sheets, which was not previously possible.