Added Api. Pocketbase. Python sdk

Api/singleton.py

@@ -0,0 +1,16 @@
+class Singleton:
+    def __init__(self, decorated):
+        self._decorated = decorated
+
+    def instance(self):
+        try:
+            return self._instance
+        except AttributeError:
+            self._instance = self._decorated()
+            return self._instance
+
+    def __call__(self):
+        raise TypeError('Singletons must be accessed through `instance()`.')
+
+    def __instancecheck__(self, inst):
+        return isinstance(inst, self._decorated)