def append_default(self, new_default_name: str) -> None:
stripped_default_name = new_default_name.strip(WS)<EOL>if stripped_default_name == self.name.strip(WS):<EOL><INDENT>return<EOL><DEDENT>dig = True<EOL>innermost_param = self<EOL>while dig:<EOL><INDENT>dig = False<EOL>default = innermost_param.default<EOL>for p in innermost_param.parameters:<EOL><INDENT>if p.string == default:<EOL><INDENT>if stripped_default_name == p.name.strip(WS):<EOL><INDENT>return<EOL><DEDENT>innermost_param = p<EOL>dig = True<EOL><DEDENT><DEDENT><DEDENT>innermost_default = innermost_param.default<EOL>if innermost_default is None:<EOL><INDENT>innermost_param.insert(-<NUM_LIT:3>, '<STR_LIT>' + new_default_name + '<STR_LIT>')<EOL><DEDENT>else:<EOL><INDENT>name = innermost_param.name<EOL>innermost_param[<EOL>len('<STR_LIT>' + name + '<STR_LIT:|>'):<EOL>len('<STR_LIT>' + name + '<STR_LIT:|>' + innermost_default)<EOL>] = '<STR_LIT>' + new_default_name + '<STR_LIT:|>' + innermost_default + '<STR_LIT>'<EOL><DEDENT>
Append a new default parameter in the appropriate place.

        Add the new default to the innter-most parameter.
        If the parameter already exists among defaults, don't change anything.

        Example:
            >>> p = Parameter('{{{p1|{{{p2|}}}}}}')
            >>> p.append_default('p3')
            >>> p
            Parameter("'{{{p1|{{{p2|{{{p3|}}}}}}}}}'")