Function ensure_single_clearable_value 

fn ensure_single_clearable_value<'a>(
    keyword: &Keyword,
    value: &'a ClearableValue,
) -> Result<&'a Option<String>, BridgeError>

Ensures that in a combination of Keyword and ClearableValue, a ClearableValue::Single is used and returns the value.

Errors

Returns an error, if value is a ClearableValue::Array.