重複する単語を削除したい

リアルタイムで収集したツイートから、url, 返信, RTを除去した後に重複行を削除したものを表示しようとしたら、このようなエラーが表示されてしましました。
エラーの該当箇所をprint(corpus)に戻すと、以下の写真のように、重複要素を持つ二次元配列の形をした重複行が出力される事を確認済みです。

写真

解決に向けてお知恵をお貸しいただけますと幸いです。宜しくお願いします。

エラー

Traceback (most recent call last):
  File "honban.py", line 140, in <module>
    stream.sample()
  File "/Users/macuser/Workspaces/jxpress/trendword/.direnv/python-3.7.3/lib/python3.7/site-packages/tweepy/streaming.py", line 449, in sample
    self._start(is_async)
  File "/Users/macuser/Workspaces/jxpress/trendword/.direnv/python-3.7.3/lib/python3.7/site-packages/tweepy/streaming.py", line 389, in _start
    self._run()
  File "/Users/macuser/Workspaces/jxpress/trendword/.direnv/python-3.7.3/lib/python3.7/site-packages/tweepy/streaming.py", line 320, in _run
    six.reraise(*exc_info)
  File "/Users/macuser/Workspaces/jxpress/trendword/.direnv/python-3.7.3/lib/python3.7/site-packages/six.py", line 693, in reraise
    raise value
  File "/Users/macuser/Workspaces/jxpress/trendword/.direnv/python-3.7.3/lib/python3.7/site-packages/tweepy/streaming.py", line 289, in _run
    self._read_loop(resp)
  File "/Users/macuser/Workspaces/jxpress/trendword/.direnv/python-3.7.3/lib/python3.7/site-packages/tweepy/streaming.py", line 351, in _read_loop
    self._data(next_status_obj)
  File "/Users/macuser/Workspaces/jxpress/trendword/.direnv/python-3.7.3/lib/python3.7/site-packages/tweepy/streaming.py", line 323, in _data
    if self.listener.on_data(data) is False:
  File "/Users/macuser/Workspaces/jxpress/trendword/.direnv/python-3.7.3/lib/python3.7/site-packages/tweepy/streaming.py", line 54, in on_data
    if self.on_status(status) is False:
  File "honban.py", line 99, in on_status
    corpus = set(corpus)
TypeError: unhashable type: 'list'

コード

renshu.py
1#上記省略
2    def on_status(self, status):
3        text = str(status.text)
4
5        #日本語ツイートをファイルに書き込んでいる + ツイートの数を表示
6        if status.lang == "ja":
7            with open("testd.txt", "a", encoding="utf-8") as f:
8                f.write(text)
9            with codecs.open("testd.txt", "r", "utf-8") as f:
10                num_lines = sum(1 for line in open("testd.txt"))#総文書数
11                corpus = f.read().split("\n")
12
13            texts=[]
14            for i in corpus:
15                texts.append(re.sub(r"http\S+", "", i))
16                texts.append(re.sub(r"@(\w+) ", "", i))
17                texts.append(re.sub(r"(^RT.*)", "", i, flags=re.MULTILINE | re.DOTALL))
18                emoji_pattern = re.compile("["
19                u"\U0001F600-\U0001F64F"
20                u"\U0001F300-\U0001F5FF"
21                u"\U0001F680-\U0001F6FF"
22                u"\U0001F1E0-\U0001F1FF"
23                "]+", flags=re.UNICODE)
24                texts.append(emoji_pattern.sub("", i))
25            texts.append(i)
26            texts = list(set(texts))
27
28　　　　mecab = MeCab('-d /usr/local/lib/mecab/dic/mecab-ipadic-neologd')
29
30            rm_list = ["RT","https","co"]
31
32            stop_words = []
33            path = 'stop_words.txt'
34            with open(path) as g:
35                stop_words = g.readlines()
36
37            docs = []
38            for txt in texts:
39                words = mecab.parse(txt, as_nodes=True)
40            doc = []
41            for w in words:
42                if w.feature.split(",")[0] == "名詞":
43                    if len(w.surface) >= 3:
44                        if w.surface not in rm_list:
45                            doc.append(w.surface)                         
46                docs.append(doc)
47            corpus = docs
48            corpus = set(corpus)
49
50	#重複した単語の削除
51            nouns = []
52            for line in corpus:
53                if line not in nouns:
54                    nouns.append(line)
55                    print(nouns)
56#下記省略