Unicode.Property.ascii_hex_digit-question-mark
You're seeing just the function
ascii_hex_digit-question-mark, go back to Unicode.Property module for more information.
Returns a boolean indicating if the
codepoint or string has the property
:ascii_hex_digit.
For string parameters, all codepoints in
the string must have the :ascii_hex_digit
property in order for the result to be true.