How to parse values from macOS extended file attributes?

If you download a file from the internet using Safari, some extended attributes are added to the downloaded file, among which com.apple.metadata:kMDItemWhereFroms which contains the original URL of the download. In Finder > Get Info the value of this key will be displayed under **Where from:**. /bin/ls -alh shows the presence of extended attributes with a @ in the mode column and xattr -l filename.zip will list all the attributes. According to the xattr's man page to print the value of an attribute one can use:

xattr -p com.apple.metadata:kMDItemWhereFroms filename.zip

# OUTPUT
# com.apple.metadata:kMDItemWhereFroms: bplist00�_=https://example.com/filename.zip 

So even if the content is visible, the value is in a binary format with a header of bplist00�_. I tried to parse it in the following way:

xattr -p com.apple.metadata:kMDItemWhereFroms filename.zip > url.plist

# checking the file format:
file url.plist

# OUTPUT:
# url.plist: Apple binary property list

# assuming this should work:
plutil -convert xml1 url.plist

# OUTPUT:
# url.plist: Property List error: Unexpected character b at line 1 / JSON error: 
# JSON text did not start with array or object and option to allow 
# fragments not set. around line 1, column 0.

Trying to parse the file with python's ootb plistlib throws an error too:

import plistlib

with open('url.plist', 'rb') as fi:
    plist = plistlib.load(fi)

# OUTPUT:
# plistlib.InvalidFileException: Invalid file

From the output it looks like it is not a regular binary plist format even though file url.plist claims it is an 'Apple binary property list'. Any hints as to what the format is and how to parse it to a plain text value?