from typing import List


def join_paths(paths: List[List[str]], separator: str = "/") -> List[str]:
    """Collect rows of strings to string.

    Args:
        paths: list of stp paths defined as list of strings
        separator: character to be used as separator

    Returns:
        list of joined stp paths
    """
    return list(map(lambda path: separator.join(path), paths))