Update use-importer.md (#2543)

* Update use-importer.md

* Update docs-2.0/nebula-importer/use-importer.md

Co-authored-by: abby.huang <78209557+abby-cyber@users.noreply.github.com>

* Update docs-2.0/nebula-importer/use-importer.md

Co-authored-by: abby.huang <78209557+abby-cyber@users.noreply.github.com>

---------

Co-authored-by: abby.huang <78209557+abby-cyber@users.noreply.github.com>

docs-2.0/nebula-importer/use-importer.md

@@ -261,13 +261,20 @@ schema:
             index: 1
           - name: gender
             type: string
+            defaultValue: "male"
           - name: phone
             type: string
             nullable: true
-          - name: wechat
+          - name: email
             type: string
             nullable: true
             nullValue: "__NULL__"
+          - name: address
+            type: string
+            nullable: true
+            alternativeIndices:
+              - 7
+              - 8
 ```
 
 |参数|默认值|是否必须|说明|
@@ -283,6 +290,8 @@ schema:
 |`files.schema.vertex.tags.props.index`|-|否|属性对应 CSV 文件中列的序号。|
 |`files.schema.vertex.tags.props.nullable`|`false`|否|属性是否可以为`NULL`，可选`true`或者`false`。|
 |`files.schema.vertex.tags.props.nullValue`|`""`|否|`nullable`设置为`true`时，属性的值与`nullValue`相等则将该属性值设置为`NULL`。|
+|`files.schema.vertex.tags.props.alternativeIndices`|-|否|当`nullable`为`false`时忽略。该属性根据索引顺序从 csv 中获取，直到不等于`nullValue`。|
+|`files.schema.vertex.tags.props.defaultValue`|-|否当`nullable`为`false`时忽略。根据`index`和`alternativeIndices`获取的所有值为`nullValue`时设置默认值。|
 
 !!! note
     CSV 文件中列的序号从 0 开始，即第一列的序号为 0，第二列的序号为 1。