class_docstr: Knowledge base controller handles all
  manages knowledge bases
class_docstr_tok: ["Knowledge","base","controller","handles","all","manages","knowledge","bases"]
docstr: Create default vector database for knowledge base, if not specified
docstr_tok: ["Create","default","vector","database","for","knowledge","base",",","if","not","specified"]
code: def _create_persistent_chroma(self, kb_name, engine="chromadb"):
      """Create default vector database for knowledge base, if not specified"""
  
      vector_store_name = f"{kb_name}_{engine}"
  
      vector_store_folder_name = f"{vector_store_name}"
      connection_args = {"persist_directory": vector_store_folder_name}
  
      # check if exists
      if self.session.integration_controller.get(vector_store_name):
          return vector_store_name
  
      self.session.integration_controller.add(
          vector_store_name, engine, connection_args
      )
      return vector_store_name
  
imports: import copy
  from typing import List
  import pandas
  import mindsdb_sql.planner.utils
  from mindsdb_sql.parser.ast import BinaryOperation, Constant, Identifier, Select, Update, Delete, Star
  from mindsdb_sql.parser.dialects.mindsdb import CreatePredictor
  import mindsdb.interfaces.storage.db
  from mindsdb.integrations.libs.vectordatabase_handler import TableField
  from mindsdb.utilities.exception import EntityExistsError, EntityNotExistsError
label_desc: Use image node_id 3 for calling the KnowledgeBaseController obj's underlying member method code with example usage: obj._create_persistent_chroma(kb_name, engine) and returns: vector_store_name, vector_store_name