Compound format creation walk-through wanted

[gleporeNARA]

NPZ is a zipped (with no compression) NumPy data array. Would like to see a simple walk-through for creating a compound signature for this format. The npy file inside the zip is described below.

Format name: NumPy Compressed Array
Version number(s): all?
PRONOM: no current signature
Extensions: npz
mime-type: application/octet-stream
Description: "The .npz file format is a zipped archive of files named after the variables they contain. The archive is not compressed and each file in the archive contains one variable in .npy format. For a description of the .npy format, see numpy.lib.format.

A simple format for saving numpy arrays to disk with the full information about them.

The .npy format is the standard binary file format in NumPy for persisting a single arbitrary NumPy array on disk. The format stores all of the shape and dtype information necessary to reconstruct the array correctly even on another machine with a different architecture. The format is designed to be as simple as possible while achieving its limited goals.

The .npz format is the standard format for persisting multiple NumPy arrays on disk. A .npz file is a zip file containing multiple .npy files, one for each array."

Format type: Text (Structured)

Vendor: https://numpy.org/

NPY format:

"A simple format for saving numpy arrays to disk with the full information about them.
The .npy format is the standard binary file format in NumPy for persisting a single arbitrary NumPy array on disk. The format stores all of the shape and dtype information necessary to reconstruct the array correctly even on another machine with a different architecture. The format is designed to be as simple as possible while achieving its limited goals.
https://numpy.org/devdocs/reference/generated/numpy.lib.format.html

The first 6 bytes are a magic string: exactly \x93NUMPY."

npz.zip