def METHOD_NAME(pr_number: int) -> str:
    """Get the base branch of a PR
    >>> get_base_branch(6412)
    '1.x'
    """
    pr_page_content = urlopen(f"https://github.com/DataDog/dd-trace-py/pull/{pr_number}").read().decode("utf-8")
    return BASE_BRANCH_PATTERN.search(pr_page_content).group(1)