input: Write a function to convert a list to a dictionary where each element is a key with the value True.
  assert list_to_dict([1, 2, 3, 4, 5]) == {1: True, 2: True, 3: True, 4: True, 5: True}
  assert list_to_dict(['a', 'b', 'c']) == {'a': True, 'b': True, 'c': True}
  assert list_to_dict([]) == {}
output: def list_to_dict(lst):
      return {element: True for element in lst}