complete implementation of dataset SDK (#2147)

### What problem does this PR solve?

Complete implementation of dataset SDK.
#1102

### Type of change


- [x] New Feature (non-breaking change which adds functionality)

---------

Co-authored-by: Feiue <10215101452@stu.ecun.edu.cn>
Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>

sdk/python/ragflow/modules/base.py

@@ -18,13 +18,17 @@ class Base(object):
                     pr[name] = value
         return pr
 
-
     def post(self, path, param):
-        res = self.rag.post(path,param)
+        res = self.rag.post(path, param)
         return res
 
-    def get(self, path, params=''):
-        res = self.rag.get(path,params)
+    def get(self, path, params):
+        res = self.rag.get(path, params)
         return res
 
+    def rm(self, path, params):
+        res = self.rag.delete(path, params)
+        return res
 
+    def __str__(self):
+        return str(self.to_json())