docs: def find_killers(self, var_def, simplified_graph=True):
          """
          Find all killers to the specified variable definition.
  
          :param ProgramVariable var_def: The variable definition.
          :param bool simplified_graph: True if we want to search in the simplified graph, False otherwise.
          :return: A collection of all killers to the specified variable definition.
          :rtype: list
          """
  
          if simplified_graph:
              graph = self.simplified_data_graph
          else:
              graph = self.data_graph
  
          if var_def not in graph:
              return []
  
          killers = []
          out_edges = graph.out_edges(var_def, data=True)
          for _, dst, data in out_edges:
              if 'type' in data and data['type'] == 'kill':
                  killers.append(dst)
  
          return killers