Function pick 

pub fn pick<T>(amount: usize, conf: Config<T>) -> Result<Vec<T>, Error>
where
    T: Clone + Eq + Hash,

Convenience wrapper for exactly one picking operation.

let picks: Vec<String> = random_picker::pick(2,
    "a=1;b=15;c=1.5".parse().unwrap()
).unwrap();
// nonrepetitive by default
assert!(picks.iter().any(|k| k == "a" || k == "c"));