def each_message query={}, ignore_neg_terms = true, &b
    each_id query, ignore_neg_terms do |id|
      yield build_message(id)
    end
  end
def each_message query={}, ignore_neg_terms = true, &b
    each_id query, ignore_neg_terms do |id|
      yield build_message(id)
    end
  end
Yield each message matching query
 The ignore_neg_terms parameter is used to display result even if
 it contains "forbidden" labels such as :deleted, it is used in
 Poll#poll_from when we need to get the location of a message that
 may contain these labels