code: def get_data(self):
          
          if not hookenv.relation_ids(self.name):
              return
  
          ns = self.setdefault(self.name, [])
          for rid in sorted(hookenv.relation_ids(self.name)):
              for unit in sorted(hookenv.related_units(rid)):
                  reldata = hookenv.relation_get(rid=rid, unit=unit)
                  if self._is_ready(reldata):
                      ns.append(reldata)
docs: Retrieve the relation data for each unit involved in a relation and,
          if complete, store it in a list under `self[self.name]`.  This
          is automatically called when the RelationContext is instantiated.
  
          The units are sorted lexographically first by the service ID, then by
          the unit ID.  Thus, if an interface has two other services, 'db:1'
          and 'db:2', with 'db:1' having two units, 'wordpress/0' and 'wordpress/1',
          and 'db:2' having one unit, 'mediawiki/0', all of which have a complete
          set of data, the relation data for the units will be stored in the
          order: 'wordpress/0', 'wordpress/1', 'mediawiki/0'.
  
          If you only care about a single unit on the relation, you can just
          access it as `{{ interface[0]['key'] }}`.  However, if you can at all
          support multiple units on a relation, you should iterate over the list,
          like::
  
              {% for unit in interface -%}
                  {{ unit['key'] }}{% if not loop.last %},{% endif %}
              {%- endfor %}
  
          Note that since all sets of relation data from all related services and
          units are in a single list, if you need to know which service or unit a
          set of data came from, you'll need to extend this class to preserve
          that information.