require 'erb'
require 'ostruct'
 
class Dummy
  def initialize
    @pictures = [
      OpenStruct.new(tags: [
        OpenStruct.new(name: 'dog'),
        OpenStruct.new(name: 'puppy')
      ]),
      OpenStruct.new(tags: [
        OpenStruct.new(name: 'animal'),
        OpenStruct.new(name: 'puppy')
      ])
    ]
  end
 
  def render
    template = ERB.new <<-EOF
    <ul>
      <% @pictures.flat_map { |pic| pic.tags.map(&:name) }.uniq.each do |name| %>
      <li>
        <%= name %>
      </li>
      <% end %>
    </ul>
    EOF
    template.result(binding)
  end
end
 
puts Dummy.new.render

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