如何在共享上下文之间共享RSpec let变量？

RSpec.describe MyClass do
  let!(:my_variable) { MyClass.new }

  it "uses the same variable instance" do
    expect(my_variable).to be_an_instance_of(MyClass)
    my_variable.some_method
  end

  it "also uses the same variable instance" do
    expect(my_variable).to be_an_instance_of(MyClass)
    my_variable.another_method
  end
end