This folder contains the genbank database. It can be copied over ftp from https://ftp.ncbi.nlm.nih.gov/genbank/
There is a lot of data there (about 1/2 a TB) in the form of hundreds of gzips. The git repo contains one (gbenv18.seq.gz) to get started - the rest should be downloaded. The gzips contain flat ascii files which are human readable - unzip one to have a look.
There is also a README.genbank in there that explains the file format in more detail.
This script iterates through the genbank folder, reads all the gzips in there and parses them into dictionaries.
Just run it to see an example of the output in dump.json