docs: def definitions(self):
          """
          Get all definitions located at the current instruction address.
  
          :return: A list of ProgramVariable instances.
          :rtype:  list
          """
  
          defs = set()
  
          if self._simplified:
              graph = self._ddg.simplified_data_graph
          else:
              graph = self._ddg.data_graph
  
          for n in graph.nodes():  # type: ProgramVariable
              if n.location.ins_addr == self._insn_addr:
                  defs.add(DDGViewItem(self._ddg, n, simplified=self._simplified))
  
          return list(defs)