In «إن الذين كذبوا شعيبًا كانوا هم الخاسرين», what is the role of «الذين»?

Defining the Subject by a Relative Pronoun: Purposes and Rhetorical Applications

• A negative particle at the end
• The relative noun serving as the subject governed by «إن»
• An imperfect verb
• A vocative particle