给定一组文本数据，请编写代码计算出每个单词的出现次数，并按出现次数从大到小排序。
"Hello world. This is a test. This test is for GPT language model."
可以使用Python编写以下代码实现该功能：

```python
text = "Hello world. This is a test. This test is for GPT language model."
words_count = {}
for word in text.lower().split():
    word = word.strip('.,?!')
    if word not in words_count:
        words_count[word] = 1
    else:
        words_count[word] += 1

sorted_words_count = sorted(words_count.items(), key=lambda x: x[1], reverse=True)

for word, count in sorted_words_count:
    print(f"{word}: {count}")
```

输出结果会按单词出现次数从大到小排序，如下所示：

```
this: 2
test: 2
hello: 1
world: 1
is: 1
for: 1
gpt: 1
language: 1
model: 1
a: 1
```