
How do I add a validation to make sure the date string being passed to the method is in the ffg. format:
```'YYYY-MM-DD'
```
if it's not, method should raise some sort of error
?
To validate a date string in the format 'YYYY-MM-DD' in Ruby, you can use the `Date.strptime` method with a format string. Here's an example of how you might write a method to validate and parse a date string:
```ruby
def validate_and_parse_date(date_string)
  if date_string.match(/^[0-9]{4}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[0
How is arc defined in TikZ?

TikZ is a powerful drawing package for LaTeX that uses MetaPost language for defining custom shapes and drawing paths. In TikZ, you can define an arc by using the arc command. Here's a basic syntax:

```latex
\draw [<options>] (<start point>) -- (<control point 1>) -| (<control point 2>) |- (<end point>) [<angle>] ;
```

To define an arc specifically, you can use the `arc` command in MetaPost language. Its syntax is as follows