From Bioinformatikpedia

The script can be found on the biocluster at /mnt/home/student/betza/scripts.

usage: [-h] -i IFILE -q QUERY
optional arguments:
 -h, --help  show this help message and exit
 -i IFILE    with created results file (default: None)
 -q QUERY    PDB id and chain of query, e.g. 1a6zA (default: None)

The input is the results file from for (Psi)Blast.

In CATH, each domain of the protein is assigned to a fold class. This means, that one query protein can have several fold classes, one for each domain. This pyhton script computes the number of fold classes that each hit has in common with the specified query. The output is a histogram histogram of the number of same fold classes per protein for all pdb hits.