def _get_version(version_info):
    """
    converts version info tuple to version string
    example:
        (0, 1, 2, 'beta', 3) returns '0.1.2-beta.3'
    """
    vi = [str(e) for e in version_info]
    suffix = ''
    if len(vi) > 3:
        suffix = '-' + '.'.join(vi[3:])
    version = '.'.join(vi[:3]) + suffix
    return version