New parser in seq 0.11.0 does not support backslash line continuation in print statements.

```python
$ ../seq/seq-0.10.3/bin/seqc run test_backslach.seq
ABC DEFGHI JKL
ABC DEFGHI JKL

$ ../seq/seq-0.11.0/bin/seqc run test_backslach.seq
test_backslach.seq:7:15: error: syntax error, unexpected '\', expecting <NAME>, <EOL>, <SPACE>.

$ cat test_backslach.seq
s = "ABC DEF" \
    "GHI JKL"

print(s)

print(
    "ABC DEF" \
    "GHI JKL"
)
```