def _get_nr_prefix(i):
for lookup_range, prefix_string in _nr_prefix_strings.items():<EOL><INDENT>if i in lookup_range:<EOL><INDENT>return prefix_string<EOL><DEDENT><DEDENT>raise ValueError("<STR_LIT>".format(i))<EOL>
Helper function for looking up the derived name prefix associated with a Unicode scalar value.

:param i: Unicode scalar value.
:return: String with the derived name prefix.