Database import error in lesson 1


Hello all,
I am doing lesson 1 with Paperspace notebook, trying to import datasets from a URL and I get an error
my problem is with this line
In [ ]: path = untar_data(URLs.PETS); path

First, I don’t know where URLs is defined but it does work when you press run on Jupyter (maybe a global var defined somewhere else?)
but when I changed the line to the URL I want, I get the following error
Downloading {URL}

    KeyError                                  Traceback (most recent call last)
    <ipython-input-9-26a4a16d8007> in <module>
    ----> 1 path = untar_data('{URL}'); path

    /opt/conda/envs/fastai/lib/python3.6/site-packages/fastai/ in untar_data(url, fname, dest, data, force_download)
        156         fname = download_data(url, fname=fname, data=data)
        157         data_dir = Config().data_path()
    --> 158         assert _check_file(fname) == _checks[url], f"Downloaded file {fname} does not match checksum expected! Remove that file from {data_dir} and try your code again."
        159, 'r:gz').extractall(dest.parent)
        160     return dest

    KeyError: {URL}

Help please?