Unicode.Property.other_id_start
You're seeing just the function
other_id_start, go back to Unicode.Property module for more information.
Returns :other_id_start or nil indicating
if the codepoint or string has the property
:other_id_start.
For string parameters, all codepoints in
the string must have the :other_id_start
property in order for the result to :other_id_start.