code: def leave_UnionTypeDefinition(self, node, *args):
      return (
          "union "
          + node.name
          + wrap(" ", join(node.directives, " "))
          + " = "
          + join(node.types, " | ")
      )
  
imports: import json
  from .visitor import Visitor, visit
label_desc: Use image node_id 31 for calling the PrintingVisitor obj's underlying member method code with example usage: obj.leave_UnionTypeDefinition(node) and returns: unknown