code: def txn_getAssociation(self, server_url, handle=None):
          
          if handle is not None:
              self.db_get_assoc(server_url, handle)
          else:
              self.db_get_assocs(server_url)
  
          rows = self.cur.fetchall()
          if len(rows) == 0:
              return None
          else:
              associations = []
              for values in rows:
                  values = list(values)
                  values[1] = self.blobDecode(values[1])
                  assoc = Association(*values)
                  if assoc.expiresIn == 0:
                      self.txn_removeAssociation(server_url, assoc.handle)
                  else:
                      associations.append((assoc.issued, assoc))
  
              if associations:
                  associations.sort()
                  return associations[-1][1]
              else:
                  return None
docs: Get the most recent association that has been set for this
          server URL and handle.
  
          str -> NoneType or Association