<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def make_attrs(attrs=None, library=None):
 """Make standard attributes to attach to xarray datasets. Parameters attrs : dict (optional) Additional attributes to add or overwrite Returns ------- dict attrs """

    default_attrs = {"created_at": datetime.datetime.utcnow().isoformat()}
    if library is not None:
        library_name = library.__name__
        default_attrs["inference_library"] = library_name
        try:
            version = pkg_resources.get_distribution(library_name).version
            default_attrs["inference_library_version"] = version
        except pkg_resources.DistributionNotFound:
            if hasattr(library, "__version__"):
                version = library.__version__
                default_attrs["inference_library_version"] = version

    if attrs is not None:
        default_attrs.update(attrs)
    return default_attrs