public DynamicBuffer<T> this[Entity entity] { get; }

Entity

Normally, you cannot write to buffers accessed using a BufferLookup instance in a parallel Job. This restriction is in place because multiple threads could write to the same buffer, leading to a race condition and nondeterministic results. However, when you are certain that your algorithm cannot write to the same buffer from different threads, you can manually disable this safety check by putting the [NativeDisableParallelForRestriction] attribute on the BufferLookup field in the Job.