def retrieve(self, value):  # type: (Any) -> Any
        """Replace placeholders with their corresponding secrets."""
        if isinstance(value, string_types):
            for key, this_value in self.secrets.items():
                value = value.replace(key, this_value)
        elif isinstance(value, MutableMapping):
            return {k: self.retrieve(v) for k, v in value.items()}
        elif isinstance(value, MutableSequence):
            return [self.retrieve(v) for k, v in enumerate(value)]
        return value
Replace placeholders with their corresponding secrets.