class Psych::Visitors::YAMLTree

def find_ivars target, is_primitive=false
  begin
    loc = target.method(:to_yaml_properties).source_location.first
    unless loc.start_with?(Psych::DEPRECATED) || loc.end_with?('rubytypes.rb')
      if $VERBOSE
        warn "#{loc}: to_yaml_properties is deprecated, please implement \"encode_with(coder)\""
      end
      return target.to_yaml_properties
    end
  rescue
    # public_method or source_location might be overridden,
    # and it's OK to skip it since it's only to emit a warning.
  end
  is_primitive ? [] : target.instance_variables
end