title: How to set a property if not exists array in neo4j
body: <p>i want to add properties in array if a value not in the array.</p>
  <pre><code>// Create a node with an array prop
  CREATE (n:Test { my_array:['a', 'b', 'c']}) RETURN n;
  </code></pre>
  <p>Here i would like check my_array values and add 'new_value' like 'd' which is not in the list.
  Please help to add this attribute.</p>