code: def visit_bool(self, node, visited_children):
      return types.tbool
  
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 7 for calling the VCFTypeConstructor obj's underlying member method code with example usage: obj.visit_bool(node, visited_children) and returns: types