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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 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