code: def pick(source, keys, *, transform=None):
    
    check = keys if callable(keys) else lambda key: key in keys
    return {key: transform(source[key]) if transform else source[key]
            for key in source if check(key)}
docs: Returns a dictionary including only specified keys from a source dictionary.
  
    :source: a dictionary
    :keys: a set of keys, or a predicate function that accepting a key
    :transform: a function that transforms the values