code: def visit_struct(self, node, visited_children):
      tstruct, _, brace, maybe_fields, brace = visited_children
      if not maybe_fields:
          return types.tstruct()
      else:
          fields = maybe_fields[0]
          return types.tstruct(**dict(fields))
  
imports: from parsimonious import Grammar, NodeVisitor
  from hail.expr.nat import NatVariable
  from .None import types
  from hail.utils.java import unescape_parsable
label_desc: Use image node_id 12 for calling the VCFTypeConstructor obj's underlying member method code with example usage: obj.visit_struct(node, visited_children) and returns: types, types