int usd_haspayload(<stage>stage, string primpath)
Returns true if the primitive has payload.
When running in the context of a node (such as a wrangle LOP), this argument can be an integer representing the input number (starting at 0) to read the stage from. The integer is equivalent to the string form referencing a particular input, e.g., "opinput:0".
The path to the primitive.
1 if the primitive has payload, or 0 otherwise.
int has_payload = usd_haspayload(0, "/geo/sphere" );