code: @Override
    public FieldVisitor visitField(int access,
                                   String name,
                                   String description,
                                   String signature,
                                   Object value) {
      assert (currentClass != null);
      if (signature == null)
        signature = description + " " + name;
      return currentClass.visitField(access, name, description,
          signature, value);
    }
docs: "Visit" a field.
  
  @param access      field access modifiers, etc.
  @param name        field name
  @param description field description
  @param signature   field signature
  @param value       field value, if any
  @return null.