TEST_DICTIONARIES = [
  {
    'name': 'billy',
    'email': 'billy@email.com',
    'purchases': [
      'purchase_id1',
      'purchase_id2'
    ]
  },
  {
    'name': 'bob',
    'email': '2bob@email.com',
    'purchases': [
      'purchase_id3'
    ]
  },
  {
    'name': 'fred',
    'email': 'fred@email.com',
    'purchases': [
      'purchase_id4',
      'purchase_id5',
      'purchase_id6'
    ]
  }
]

TEST_INTEGER_LIST = [1, 3, 5, 1, 9, 2, 3, 7, 1]

## Problem 1: Write a function that takes a list of dictionaries and a function
## and returns another list of dictionaries, sorted by the key(s) specified in that function

## Problem 2: Write a function that takes a list of dictionaries, and returns a list
## of values such that each value in the list is a corresponding value from the corresponding dictionary

## Problem 3: Write a function that takes a list of integers, and returns double the sum of non-duplicate values
## from the list (For TEST_INTEGER_LIST, this should return 54)