Detailed Instructions: This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.
Q: The books written later in the Abbasid period in Iran are more anti Umayyad. Iran was Sunni at the time. There was much anti Arab feeling in Iran after the fall of the Persian empire. This anti Arab feeling also influenced the books on Islamic history. Al-Tabri was also written in Iran during that period. Al-Tabri was a huge collection including all the text that he could find, from all the sources. It was a collection preserving everything for future generations to codify and for future generations to judge if it was true or false.
A:
In the later Abbasid era, what branch of Islam did Iran adhere to?