When stepping through a multiline expression like this:

```
print(slug
      .replace("_", " ")
      .title()
      .upper()
      .replace("a", "b")
      .lower()
      .replace("The ", "the "))
```

only these lines are hit by the tracer function:

15 print(slug
16       .replace("_", " ")
19       .replace("a", "b")
21       .replace("The ", "the "))

I'm guessing the problem is that there are no expressions on the other lines, as the attributes and calls all start with slug.

I just came across https://www.python.org/dev/peps/pep-0626/, seems like this would need to be fixed to satisfy the PEP, but on the latest CPython it's not:

```
➜  ~ python3.10 ~/Downloads/trace_skipping_lines_bug.py
14 slug = "doing_the_thing"
15 print(slug
16       .replace("_", " ")
15 print(slug
19       .replace("a", "b")
15 print(slug
21       .replace("The ", "the "))
15 print(slug
doing the thing
➜  ~ python3.10 --version                              
Python 3.10.0a6+
➜  ~ python3.10          
Python 3.10.0a6+ (heads/master:cd8dcbc, Mar 14 2021, 11:58:23) [GCC 7.5.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> 
```

New changeset d48848c83e0f3e41b65c8f741f3fb6dbce5b9c29 by Mark Shannon in branch 'master':
bpo-39316: Make sure that attribute accesses and stores, including method calls, conform to PEP 626. (GH-24859)
https://github.com/python/cpython/commit/d48848c83e0f3e41b65c8f741f3fb6dbce5b9c29