from typing import Iterable
from typing import List


def _resplit(parts: Iterable[str]) -> List[str]:
    """
    Given a list of strings, returns a list of lines, by splitting each string
    into multiple lines where it contains newlines.

    >>> _resplit([])
    []
    >>> _resplit(['a', 'b'])
    ['a', 'b']
    >>> _resplit(['a', 'b\\nc\\nd'])
    ['a', 'b', 'c', 'd']
    """
    return [line for part in parts for line in part.splitlines()]