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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _try_free_lease(self, shard_state, slice_retry=False):
 """Try to free lease. A lightweight transaction to update shard_state and unset slice_start_time to allow the next retry to happen without blocking. We don't care if this fails or not because the lease will expire anyway. Under normal execution, _save_state_and_schedule_next is the exit point. It updates/saves shard state and schedules the next slice or returns. Other exit points are: 1. _are_states_consistent: at the beginning of handle, checks if datastore states and the task are in sync. If not, raise or return. 2. _attempt_slice_retry: may raise exception to taskqueue. 3. _save_state_and_schedule_next: may raise exception when taskqueue/db unreachable. This handler should try to free the lease on every exceptional exit point. Args: shard_state: model.ShardState. slice_retry: whether to count this as a failed slice execution. """

    @db.transactional
    def _tx():
      fresh_state = model.ShardState.get_by_shard_id(shard_state.shard_id)
      if fresh_state and fresh_state.active:
        # Free lease.
        fresh_state.slice_start_time = None
        fresh_state.slice_request_id = None
        if slice_retry:
          fresh_state.slice_retries += 1
        fresh_state.put()
    try:
      _tx()
    # pylint: disable=broad-except
    except Exception, e:
      logging.warning(e)
      logging.warning(
          "Release lock for shard %s failed. Wait for lease to expire.",
          shard_state.shard_id)