Clears the port preview for the specified port.
The port preview is hidden from the graph canvas until a new value is set using PortReference.SetPreview. If the provided port ID does not correspond to any port in the graph, any stored preview data for that port is removed and the call has no further effect. Throws ObjectDisposedException when you access this method after you call Context.Dispose on the context.
context.GetPortReference(portID).ClearPreview();