def load_users(ids_file):
    """
    Load all user IDs into a list.

        Note: The input file must be a plain text file where each line contains
        only a single unique Twitter user ID.

    Parameters:
    -----------
    - ids_file (str) : the full path to the Twitter user IDs file that you'd like to load

    Returns:
    ----------
    - users (list) : a list of Twitter user IDs
    """

    with open(ids_file, 'r') as f:
        users = [x.strip('\n') for x in f.readlines()]

    return users