int usd_isrelationship(<stage>stage, string primpath, string name)
This function checks whether the primitive has a relationship of a given name.
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.
The relationship name.
1 if the primitive has such a relationship, or
// Check if the cube has a relationship "some_relationship". int is_valid_relationship = usd_isrelationship(0, "/geo/cube", "some_relationship");