How to enumerate elements of FieldTable

[alllel]

Is there a way to list/enumerate/iterate over keys in FieldTable?
You see: FieldTable is necessary not only to send messages, but it also belongs to received messages.
And sometimes it would be nice to inspect it in detail.

I see that internally there is just a HashMap, but it is not public.

What if to add to FieldTable something like:

impl FieldTable {
  pub fn keys(&self) {
   self.1.keys()
  }
}

[gftea]

We can implement AsRef, something like below, would you like to submit a PR for this?

impl AsRef<HashMap<FieldName, FieldValue>> for FieldTable {
   fn as_ref(&self) -> &HashMap<FieldName, FieldValue> {
}
}