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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def relativize_path(path, base, os_sep=os.sep):
    '''
    Make absolute path relative to an absolute base.

    :param path: absolute path
    :type path: str
    :param base: absolute base path
    :type base: str
    :param os_sep: path component separator, defaults to current OS separator
    :type os_sep: str
    :return: relative path
    :rtype: str or unicode
    :raises OutsideDirectoryBase: if path is not below base
    '''
    if not check_base(path, base, os_sep):
        raise OutsideDirectoryBase("%r is not under %r" % (path, base))
    prefix_len = len(base)
    if not base.endswith(os_sep):
        prefix_len += len(os_sep)
    return path[prefix_len:]