docstr: Close any existing connections
  Should switch self.is_connected.
docstr_tok: ["Close","any","existing","connections","Should","switch","self.is_connected","."]
code: def disconnect(self):
      """Close any existing connections
      Should switch self.is_connected.
      """
  
      if self.is_connected is False:
          return
      try:
          self.connection.close()
          self.is_connected = False
      except Exception as e:
          logger.error(f"Error while disconnecting to CrateDB, {e}")
  
      return
  
imports: from collections import OrderedDict
  from typing import Optional
  from mindsdb_sql.parser.ast.base import ASTNode
  from mindsdb.integrations.libs.base import DatabaseHandler
  from mindsdb.utilities import log
  from mindsdb_sql import parse_sql
  from mindsdb_sql.render.sqlalchemy_render import SqlalchemyRender
  from mindsdb.integrations.libs.response import HandlerStatusResponse, HandlerResponse, RESPONSE_TYPE
  from mindsdb.integrations.libs.const import HANDLER_CONNECTION_ARG_TYPE
  import pandas
  from crate import client
  from crate.client.sqlalchemy.dialect import CrateDialect
label_desc: Use image node_id 3 for calling the CrateHandler obj's underlying member method code with example usage: obj.disconnect() without return types