from typing import List


def prepend_escape_character(escape_character_list: List[str], keyword: str) -> str:
    """Add escape character.

    If the argument 'keyword' contains the characters specified in 'escape_character_list',
    an escape character is added to the target character.

    Args:
        escape_character_list (list(str)): Give escape characters to the characters in this list
        keyword (str): String to be converted

    Returns:
        str: Returns 'keyword' after conversion.

    """
    return "".join(["\\" + x if x in escape_character_list else x for x in list(keyword)])