Some ideas about implementations
Based on the idea stated in this serde issue:
https://github.com/serde-rs/serde/issues/553
+
+## TODO
+
+* [ ] Deserialize an empty string as `None`
+* Chrono
+ * [ ] Like `ts_seconds` but for milli/nano-seconds
+ * [ ] Flexible number of digits for subsecond precision
+* [ ] Stringify `true/false`, `True/False` (for Python)
+* [ ] Derserialize a String which is itself Json, Yaml, etc.
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