Fetch all names in a namespace that should be indexed.
        Data is saved in data/ directory

def fetch_namespace():
    """
        Fetch all names in a namespace that should be indexed.
        Data is saved in data/ directory
    """
    resp = blockstack.lib.client.get_all_names(hostport=blockstack_indexer_url)
    subdomain_names = blockstack.lib.subdomains.get_all_subdomains()

    all_names = list(resp) + list(subdomain_names)

    with open(SEARCH_BLOCKCHAIN_DATA_FILE, 'w') as fout:
        fout.write(json.dumps(all_names))