from typing import List
import re


def _split_line(line: str) -> List[str]:
    """
    >>> _split_line('%%testcell test_cell1 # hello')
    ['test_cell1']
    >>> _split_line('%%testcell -n # test_cell1')
    []
    """
    positional_args = [
        arg for arg in re.split(r" +", line) if not re.match(r"^(%|-)", arg) and arg
    ]
    if "#" in positional_args:
        del positional_args[positional_args.index("#") :]

    return positional_args