Why is arg of parse_string list of string?

[ogata-k]

Why is arg of parse_string list of string? Can covert to use string?

// cli/scanner.rs
fn parse_string(subs: &[String]) -> Result<String, ScannerError> {
if subs.is_empty() {
return Ok(String::default());
} else {
if subs.len() != 1 {
return Err(ScannerError::UnknownStringFormat(subs.to_vec()));
} else {
return Ok(subs[0].to_string());
}
}
}