如何删除包含未知字符的子串的所有出现？

def remove_unknown_substring(string, unknown_char):
    start_index = 0
    while start_index < len(string):
        index = string.find(unknown_char, start_index)
        if index == -1:
            break
        end_index = index + len(unknown_char)
        string = string[:index] + string[end_index:]
        start_index = index
    return string

# 示例用法
original_string = "abc?def?ghi?jkl?mno"
unknown_char = "?"
result = remove_unknown_substring(original_string, unknown_char)
print(result)