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+# How it works
+
+## create object with json string as value
+
+```python
+>>> o = {"foo": "foo"}
+>>> oo = {"bar": json.dumps(o)}
+>>> oo
+{'bar': '{"foo": "foo"}'}
+>>> json.dumps(oo)
+'{"bar": "{\\"foo\\": \\"foo\\"}"}'
+```
+
+## extract the escaped string
+
+```python
+>>> s = json.dumps(oo)[9:-2]
+>>> s
+'{\\"foo\\": \\"foo\\"}'
+```
+
+## reproduce error
+
+```python
+>>> r = json.loads(s)
+Traceback (most recent call last):
+  File "<stdin>", line 1, in <module>
+  File "/usr/lib/python3.10/json/__init__.py", line 346, in loads
+    return _default_decoder.decode(s)
+  File "/usr/lib/python3.10/json/decoder.py", line 337, in decode
+    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
+  File "/usr/lib/python3.10/json/decoder.py", line 353, in raw_decode
+    obj, end = self.scan_once(s, idx)
+json.decoder.JSONDecodeError: Expecting property name enclosed in double quotes: line 1 column 2 (char 1)
+```
+
+## solve error by nesting json
+
+```python
+>>> r = json.loads('{"foo": "' + s + '"}')
+>>> r
+{'foo': '{"foo": "foo"}'}
+>>> json.loads(r["foo"])
+{'foo': 'foo'}
+```