join.  If the optional second argument sep is absent or None,
    runs of whitespace characters are replaced by a single space
    and leading and trailing whitespace are removed, otherwise
    sep is used to split and join the words.
    """
    return (sep or ' ').join(map(str.capitalize, s.split(sep)))
####################################################################
import re as _re
from collections import ChainMap as _ChainMap
_sentinel_dict = {}
class Template:
    """A string class for supporting $-substitutions."""
    delimiter = '$'
    # r'[a-z]' matches to non-ASCII letters when used with IGNORECASE, but
    # without the ASCII flag.  We can't add re.ASCII to flags because of
    # backward compatibility.  So we use the ?a local flag and [a-z] pattern.
    # See https://bugs.python.org/issue31672
    idpattern = r'(?a:[_a-z][_a-z0-9]*)'
    braceidpattern = None
    flags = _re.IGNORECASE
    def __init_subclass__(cls):
        super().__init_subclass__()
        if 'pattern' in cls.__dict__:
            pattern = cls.pattern
        else:
            delim = _re.escape(cls.delimiter)
            id = cls.idpattern
            bid = cls.braceidpattern or cls.idpattern
            pattern = fr"""
            {delim}(?:
              (?P<escaped>{delim})  |   # Escape sequence of two delimiters
              (?P<named>{id})       |   # delimiter and a Python identifier
              {{(?P<braced>{bid})}} |   # delimiter and a braced identifier
              (?P<invalid>)             # Other ill-formed delimiter exprs
            )
            """