Operation constructor Null safety

Implementation

const Operation(
  this.method, [
  String? pathVariable1,
  String? pathVariable2,
  String? pathVariable3,
  String? pathVariable4,
])  : _pathVariable1 = pathVariable1,
      _pathVariable2 = pathVariable2,
      _pathVariable3 = pathVariable3,
      _pathVariable4 = pathVariable4;