import json
import sys

backend_spec = sys.argv[1]
backend_obj = sys.argv[2] if len(sys.argv) >= 3 else None

backend = __import__(backend_spec, fromlist=[None])
if backend_obj:
    backend = getattr(backend, backend_obj)

for_build_requires = backend.get_requires_for_build_sdist(None)
output = json.dumps(for_build_requires)
print(output)
