 Complete the following phrase:  Principal photography began on 2 May and wrapped on 1 December 2005. After its completion, director Alejandro González Iñárritu and screenwriter Guillermo Arriaga had a falling-out regarding the authorship of their previous film, 21 Grams. Arriaga argued that cinema is a collaborative medium, and that both he and González Iñárritu are thus the authors of the films they have worked on together. González Iñárritu claimed sole credit as the auteur of those same films, minimizing Arriagas contribution to the pictures. Following this dispute, González Iñárritu banned Arriaga from attending the 