Checks if a value is a Slot.
Constraint keys are not admitted: they are merged into the entry hosting the slot, so an entry carrying both is validated through isQuery instead.
The value to check
True if value is a valid Cell or Projection; false otherwise
value
Checks if a value is a Slot.
Constraint keys are not admitted: they are merged into the entry hosting the slot, so an entry carrying both is validated through isQuery instead.