Given a list of strings with words separated by spaces,
create a single list of all the words.

input = [
  'ab cde',
  'x yz qwerty',
  'abc x cde abc d er'
]

output = ['ab', 'cde','x', 'yz', 'qwerty', 'abc', 'x', 'cde', 'abc', 'd', 'er']

Then create a list of unique values:

output = ['ab', 'cde','x', 'yz', 'qwerty', 'x', 'd', 'er']