code: def visit_Constant(self, node):
      node = self.generic_visit(node)
      var = self.const.get(node.value)
      if var is not None:
          node = ast.Name(id=var, ctx=ast.Load())
      return node
  
file_path: funsor/funsor/syntax.py
imports: import ast
  import functools
  import inspect
  from .None import ops
label_desc: Use image node_id 2 for calling the OpTransformer obj's underlying member method code with example usage: obj.visit_Constant(node) and returns: node