For example, if the current project uses inches, this function will return `(1/25.4)`. If the current project uses millimeters, this function will return `1`.
**Caution**: This function is only intended to be used when you absolutely MUST have different units in your code than the project settings. Otherwise, it is a bad pattern to use this function.
We merely provide these functions for convenience and readability, as `10 * mm()` is more readable that your intent is "I want 10 millimeters" than `10 * (1/25.4)`, if the project settings are in inches.
