DOCUMENTATION:
  name: union
  author: Brian Coca (@bcoca)
  version_added: "1.4"
  short_description: union of lists
  description:
    - Provide a unique list of all the elements of two lists.
  options:
    _input:
      description: A list.
      type: list
      required: true
    _second_list:
      description: A list.
      type: list
      required: true
  seealso:
    - plugin_type: filter
      plugin: ansible.builtin.difference
    - plugin_type: filter
      plugin: ansible.builtin.intersect
    - plugin_type: filter
      plugin: ansible.builtin.symmetric_difference
    - plugin_type: filter
      plugin: ansible.builtin.unique
EXAMPLES: |
  # return the unique elements of list1 added to list2
  # list1: [1, 2, 5, 1, 3, 4, 10]
  # list2: [1, 2, 3, 4, 5, 11, 99]
  {{ list1 | union(list2) }}
  # => [1, 2, 5, 1, 3, 4, 10, 11, 99]
RETURN:
  _value:
    description: A unique list of all the elements from both lists.
    type: list