code: func (t *Transaction) Count(c *Collection, count *int) {
  	if c == nil {
  		t.setError(newNilCollectionError("Count"))
  		return
  	}
  	if !c.index {
  		t.setError(newUnindexedCollectionError("Count"))
  		return
  	}
  	t.Command("SCARD", redis.Args{c.IndexKey()}, NewScanIntHandler(count))
  }
docs: // Count counts the number of models of the given type in the database in an existing
  // transaction. It sets the value of count to the number of models. Any errors
  // encountered will be added to the transaction and returned as an error when the
  // transaction is executed.