Returns a flat list of all the keys in a flat dictionary.

Use dict.keys() to return the keys in the given dictionary. Return a list() of the previous result.

def keys_only(flat_dict):
  return list(flat_dict.keys())

ages = {
  "Peter": 10,
  "Isabel": 11,
  "Anna": 9,
}
keys_only(ages) # ['Peter', 'Isabel', 'Anna']