flatMap 
flatMap(items) => a 
| Parameter | Type | Description | 
|---|---|---|
| items | Iterable | 
Returns 
(Generator) A list of flattened values where the closure has been called on each value.
Example 
elk
["abc", "def"] | flatMap => x: x  #=> ["a", "b", "c", "d", "e", "f"]["abc", "def"] | flatMap => x: x  #=> ["a", "b", "c", "d", "e", "f"]