The default implementation collects the Display value into a String
and then passes that to Serializer::serialize_str when the std or collections
features are enabled, otherwise it unconditionally returns an error.
This function serializes the given iterator as a sequence. Its iter parameter
has type I: IntoIterator, <I as IntoIterator>::Item: Serialize, which means it
will work both for iterators passed by value, therefore consuming them, and as
the value for a #[serde(serialize_with)] attribute, where it will be called as
Serializer::collect_seq(&self.field, serializer), relying on the common practice
of implementing IntoIterator for &C where C is a data type representing some
kind of collection.
Anthony Ramine