lib/htmless/abstract.rb
def set_variables(instance_variables)
      instance_variables.each { |name, value| instance_variable_set("@#{name}", value) }
      yield(self)
      instance_variables.each { |name, _| remove_instance_variable("@#{name}") }
      self
    end
def set_variables(instance_variables)
      instance_variables.each { |name, value| instance_variable_set("@#{name}", value) }
      yield(self)
      instance_variables.each { |name, _| remove_instance_variable("@#{name}") }
      self
    end
sets instance variables when block is yielded
 @param [Hash{String => Object}] instance_variables hash of names and values to set
 @yield block when variables are set, variables are cleaned up afterwards