create dataset (#2074)

### What problem does this PR solve?

You can use sdk to create a dataset

### Type of change

- [x] New Feature

---------

Co-authored-by: root <root@xwg>

sdk/python/ragflow/modules/base.py

@@ -0,0 +1,30 @@
+class Base(object):
+    def __init__(self, rag, res_dict):
+        self.rag = rag
+        for k, v in res_dict.items():
+            if isinstance(v, dict):
+                self.__dict__[k] = Base(rag, v)
+            else:
+                self.__dict__[k] = v
+
+    def to_json(self):
+        pr = {}
+        for name in dir(self):
+            value = getattr(self, name)
+            if not name.startswith('__') and not callable(value) and name != "rag":
+                if isinstance(value, Base):
+                    pr[name] = value.to_json()
+                else:
+                    pr[name] = value
+        return pr
+
+
+    def post(self, path, param):
+        res = self.rag.post(path,param)
+        return res
+
+    def get(self, path, params=''):
+        res = self.rag.get(path,params)
+        return res
+
+