Function MemoryContextIsValid 

pub unsafe fn MemoryContextIsValid(context: MemoryContext) -> bool

Returns true if memory context is tagged correctly according to Postgres.

Safety

The caller must only attempt this on a pointer to a Node. This may clarify if the pointee is correctly-initialized pg_sys::MemoryContextData.

Implementation Note

If Postgres adds more memory context types in the future, we need to do that here too.