code: func (c *cursor) Prev() bool {
  	// Ensure transaction state is valid.
  	if err := c.bucket.tx.checkClosed(); err != nil {
  		return false
  	}
  
  	// Nothing to return if cursor is exhausted.
  	if c.currentIter == nil {
  		return false
  	}
  
  	// Move the current iterator to the previous entry and choose the
  	// iterator that is both valid and has the larger key.
  	c.currentIter.Prev()
  	return c.chooseIterator(false)
  }
docs: // Prev moves the cursor one key/value pair backward and returns whether or not
  // the pair exists.
  //
  // This function is part of the database.Cursor interface implementation.