def [](property)
      assert_property_exists! property
      value = super(property)
      # If the value is a lambda, proc, or whatever answers to call, eval the thing!
      if value.is_a? Proc
        self[property] = value.call # Set the result of the call as a value
      else
        yield value if block_given?
        value
      end
    end
def [](property)
      assert_property_exists! property
      value = super(property)
      # If the value is a lambda, proc, or whatever answers to call, eval the thing!
      if value.is_a? Proc
        self[property] = value.call # Set the result of the call as a value
      else
        yield value if block_given?
        value
      end
    end
Retrieve a value from the Dash (will return the
 property's default value if it hasn't been set).