from typing import Set


def file_to_set(file_name: str) -> Set[str]:
    """
    Loads a file to a set.

    :returns: the lines of the file in a ``set``, an empty ``set`` if
              _file_name_ is ``None``.
    """
    if file_name:
        with open(file_name, 'rt') as inf:
            set_from_file = set(line.strip() for line in inf)
    else:
        set_from_file = set()
    return set_from_file