fn indent(s: &str, depth: usize) -> String {
    let indent = format!("{:depth$}", "", depth = depth);

    s.split('\n')
        .map(|line| {
            let mut result = String::new();
            if line.chars().any(|c| !c.is_whitespace()) {
                result.push_str(&indent);
                result.push_str(line);
            }
            result
        })
        .collect::<StdVec<_>>()
        .join(NEW_LINE_SEPARATOR)
}
Indents a given string to a given depth. Depth is given in number of spaces
to be appended. Returns a new string with the new indentation. Will not
indent whitespace lines.

# Parameters

* `s` - The string to indent.
* `depth` - The depth to indent the lines to, in spaces.

# Returns

The indented string.
src/describe/stub.rs