Ensure data structures are accurately represented with their proper constraints and valid implementations, particularly for recursive structures. When documenting or implementing collections: 1. Explicitly state data structure constraints - For set-like structures, clearly document hashability requirements - For tree-like structures, describe node relationships precisely 2. Validate that recursive type examples actually terminate - Include escape conditions in recursive type definitions - Ensure examples represent structures that can be instantiated ```python # Incorrect recursive type definition (infinite recursion) type B = list[C] type C = B # No termination condition! # Correct recursive type definition with termination type A = list[A] | None # Terminates with None ``` Properly defined data structures not only prevent runtime errors but also enable more efficient algorithm implementations.