class GraphQL::Language::Visitor

def visit
  # `@document` may be any kind of node:
  visit_method = :"#{@document.visit_method}_with_modifications"
  result = public_send(visit_method, @document, nil)
  @result = if result.is_a?(Array)
    result.first
  else
    # The node wasn't modified
    @document
  end
end