# 第 15_05 题 AI / Agent：从事件流中提取文字片段
# 实现 text_pieces(events) 生成器。events 中每项保证是字典；只 yield kind 为 "text" 且 content 为非空字符串的内容，跳过其他项。用 [{"kind":"start"}, {"kind":"text","content":"Py"}, {"kind":"usage","content":3}, {"kind":"text","content":"thon"}] 生成片段并拼接打印。
# 预期程序输出：
# Python

def text_pieces(events):
    for event in events:
        if event.get("kind") != "text":
            continue
        content = event.get("content")
        if isinstance(content, str) and content != "":
            yield content

events = [
    {"kind": "start"},
    {"kind": "text", "content": "Py"},
    {"kind": "usage", "content": 3},
    {"kind": "text", "content": "thon"},
]
print("".join(text_pieces(events)))