Function unescapePattern

unescapePattern(pattern?: null | string): undefined | null | string
Returns a regex pattern that unescaped the given pattern
Parameters
- Optionalpattern: null | string
  The pattern to inspect
Returns undefined | null | string
a regex pattern that unescaped the given pattern
Author
David Hsing
Example
```
unescapePattern('\\\\');    // '\\'
unescapePattern('\\+\\-=');    // '+-='
```