feat: limit there to be only one line between two nodes #918 (#1310)

### What problem does this PR solve?

feat: limit there to be only one line between two nodes #918

### Type of change

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

web/src/pages/flow/utils.ts

@@ -3,13 +3,9 @@ import { removeUselessFieldsFromValues } from '@/utils/form';
 import dagre from 'dagre';
 import { curry, isEmpty } from 'lodash';
 import pipe from 'lodash/fp/pipe';
-import { Connection, Edge, MarkerType, Node, Position } from 'reactflow';
+import { Edge, MarkerType, Node, Position } from 'reactflow';
 import { v4 as uuidv4 } from 'uuid';
-import {
-  Operator,
-  RestrictedUpstreamMap,
-  initialFormValuesMap,
-} from './constant';
+import { Operator, initialFormValuesMap } from './constant';
 import { NodeData } from './interface';
 
 const buildEdges = (
@@ -170,11 +166,3 @@ export const buildDslComponentsByGraph = (
 export const getOperatorTypeFromId = (id: string | null) => {
   return id?.split(':')[0] as Operator | undefined;
 };
-
-// restricted lines cannot be connected successfully.
-export const isValidConnection = (connection: Connection) => {
-  const ret = RestrictedUpstreamMap[
-    getOperatorTypeFromId(connection.source) as Operator
-  ]?.every((x) => x !== getOperatorTypeFromId(connection.target));
-  return ret;
-};