code: def get_instances_by_tag(self, tags):
          
  
          try:
              c = ec2.connect_to_region(self._region,
                                        aws_access_key_id=self._aws_access_key_id,
                                        aws_secret_access_key=self._aws_secret_access_key)
  
              # select instance by list of tags (OR used)
              reservations = c.get_all_reservations(filters=SergentSsh.tags_to_dict(tags))
              instances = list()
  
              for r in reservations:
                  # for each instance launched by this reservation
                  for instance in r.instances:
                      # we need only running instances
                      if instance.state.lower() == 'running':
                          instances.append(instance)
  
              return instances
          except NoAuthHandlerFound:
              raise SergentSshException('Boto said that you should check your credentials')
docs: :param tags:list of tags you to connect to (tagname=value)
          :return: instance list