In this example, I try to think of how I can deal with errors
```
> "hello
-> unfinished quote "

create a concept to recognize the error

> def concept unfinished quote q
... where:
...... q in ('"', '"')
... desc:
...... "Error detected by the default parser where the trailing quote is missing"
... input = sheerka.last_input


Create the rule to manage the error

> when unfinished quote q as c:
... add rule r as:
...... if q is last of sheerka.input:
......... sheerka.resume(c, c.input + input)
......... remove r 

def concept a is last of b as:
    where b is list
    as b[-1] == a
```