import re


def strip_version(arxiv_id):
    """
    Remove the version suffix from an arXiv id.

    :param arxiv_id: The (canonical) arXiv ID to strip.
    :returns: The arXiv ID without the suffix version

    >>> strip_version('1506.06690v1')
    '1506.06690'

    >>> strip_version('1506.06690')
    '1506.06690'
    """
    return re.sub(r"v\d+\Z", '', arxiv_id)