Bug

The slides presentations get smoketest fails because the Google Discovery Document for presentations.get has a mismatch between flatPath placeholder names and actual parameter names:

• path: v1/presentations/{+presentationId} ✅ matches parameter name
• flatPath: v1/presentations/{presentationsId} ❌ uses plural presentationsId

build_url() unconditionally prefers flatPath over path, so the placeholder {presentationsId} never matches the user-supplied presentationId parameter, resulting in:

Path parameter 'presentationId' was provided but is not present in URL template 'v1/presentations/{presentationsId}'

Repro

gws slides presentations get \
  --params '{"presentationId": "1knOKD_87JWE4qsEbO4r5O91IxTER5ybBBhOJgZ1yLFI", "fields": "presentationId,slides(objectId)"}' \
  | jq -e '.presentationId'
# Returns null / exit code 1

Fix

Add a fallback in build_url(): if flatPath placeholders don't match any path parameters, fall back to path (which uses RFC 6570 {+var} operators that the code already handles).