docs: def get_relationships(manager, handle_id1, handle_id2, rel_type=None, legacy=True):
      """
      Takes a start and an end node with an optional relationship
      type.
      Returns the relationships between the nodes or an empty list.
      """
      if rel_type:
          q = """
          MATCH (a:Node {{handle_id: {{handle_id1}}}})-[r:{rel_type}]-(b:Node {{handle_id: {{handle_id2}}}})
          RETURN collect(r) as relationships
          """.format(rel_type=rel_type)
      else:
          q = """
              MATCH (a:Node {handle_id: {handle_id1}})-[r]-(b:Node {handle_id: {handle_id2}})
              RETURN collect(r) as relationships
              """
      with manager.session as s:
          if legacy:
              relationships = s.run(q, {'handle_id1': handle_id1, 'handle_id2': handle_id2}).single()['relationships']
              return [relationship.id for relationship in relationships]
          return s.run(q, {'handle_id1': handle_id1, 'handle_id2': handle_id2}).single()['relationships']