python packages which is not required by others (like `brew leaves`)

conda-leaves.py

#!/usr/bin/env python3
import os
import json
import glob
import subprocess

files = glob.glob(os.path.expanduser('~/miniconda3/pkgs/cache/*.json'))
deps = {}
for f in files:
    j = json.load(open(f))
    for pkg, info in j['packages'].items():
        pkg = '-'.join(pkg.split('-')[:-2]).replace('-', '_')
        deps[pkg] = [d.split()[0] for d in info['depends']]
installed = subprocess.getoutput('conda list | tail -n +3 | cut -d " " -f 1')
installed = set(installed.split('\n'))
required = set(dep for dep in deps[pkg] for pkg in installed)
print('\n'.join(installed - required))