/// An attribute is a key-value data, where value is generic.
///
/// It will allow external system to filter [`Log`](struct.Log.html) list
/// thanks to this attributes. Due to this, the value will be casted to String
/// later, thanks to [`as_string(&self)`](trait.ValueAsString.html).
///
/// # See also
///
/// [`ValueAsString`](trait.ValueAsString.html)
/// A short-hand for [`Attribute`](struct.Attribute.html)
pub type Attr<T> = ;