code: def str(self):
      if self.operator is None:
          assert len(self.items) == 1 and isinstance(self.items[0], str)
          return self.items[0]
      else:
          assert isinstance(self.operator, str)
          return (
              self.operator
              + "("
              + ", ".join([str(item) for item in self.items])
              + ")"
          )
  
imports: from __future__ import print_function
  from __future__ import division
  import re
  import sys
label_desc: Use image node_id 3 for calling the Descriptor obj's underlying member method code with example usage: obj.str() and returns: self, unknown