premise: Margarita la tornera (Margarita the Gatekeeper) is an opera in three acts composed by Ruperto Chapí to a libretto by Carlos Fernández Shaw, based on a dramatic poem by José Zorrilla. It premiered on February 24, 1909 at the Teatro Real in Madrid in a performance conducted by the composer. An acclaimed recording of the opera came out in 1999 with Plácido Domingo and Elisabete Matos.
hypothesis: Jose Zorilla's poem was created after the opera.
reason: The opera was based off the poem so the poem had to have been created before the opera. I think the AI got confused because of the partial sentence about the poem that was tacked onto the end of the opera's main line.