code: def get_default_contact(self, client=None):
          
          catalog = api.get_tool("portal_catalog")
          client = client or self.get_client()
          path = api.get_path(self.context)
          if client:
              path = api.get_path(client)
          query = {
              "portal_type": "Contact",
              "path": {
                  "query": path,
                  "depth": 1
              },
              "incactive_state": "active",
          }
          contacts = catalog(query)
          if len(contacts) == 1:
              return api.get_object(contacts[0])
          return None
docs: Logic refactored from JavaScript:
  
          * If client only has one contact, and the analysis request comes from
          * a client, then Auto-complete first Contact field.
          * If client only has one contect, and the analysis request comes from
          * a batch, then Auto-complete all Contact field.
  
          :returns: The default contact for the AR
          :rtype: Client object or None