etree bug function namespace prefix

etree_test.ipynb

test.py

from lxml import etree

etree.FunctionNamespace("http://exslt.org/regular-expressions").prefix = 're'

text = """
<monthEntity month="02" year="1998">
    <article>
        <full_text> Some article text </full_text>
        <full_text> Some more article text fragment 2 </full_text>
    </article>
</monthEntity>
"""
t = etree.fromstring(text)
search = etree.XPath('//full_text[re:match(text(), "fragment")]')
search(t) # this one works. returns a list with 1 element
search(t) # this one fails with 
# src/lxml/xpath.pxi in lxml.etree.XPath.__call__ (src/lxml/lxml.etree.c:172853)()
# ...
# XPathFunctionError: XPath function '{�{|
}match' not found

# The thing before `match` in curly braces sometimes changes on different runs of the program
# So this could be a bug somewhere
# using etree.__version__ 3.7.2