[design doc] fix clustering model on sqlflow (#763)
[design doc] fix clustering model on sqlflow (#763)

* Fix executor test

* Design: Clustering in SQLflow

* fix:Design of Clustering in SQLflow

* cluster_model_train_overview.png

* fix 2.0 Design: Clustering in SQLflow

* fix2.0 Design: Clustering in SQLflow

* fix3.0 Design: Clustering in SQLflow

* modify cluster_model_train_overview.png

* fix 3.1 Design: Clustering on SQLflow

* fix 3.2 Design: Clustering on SQLflow

* fix 3.3 Design: Clustering on SQLflow

sql-machine-learning/sqlflow,sql-machine-learning/sqlflow,sql-machine-learning/sqlflow,sql-machine-learning/sqlflow,sql-machine-learning/sqlflow,sql-machine-learning/sqlflow