docstr: Set up any connections required by the handler
  Should return output of check_connection() method after attempting
  connection. Should switch self.is_connected.
  Returns:
      Connection Object
docstr_tok: ["Set","up","any","connections","required","by","the","handler","Should","return","output","of","check_connection","(",")","method","after","attempting","connection",".","Should","switch","self.is_connected",".","Returns",":","Connection","Object"]
code: def connect(self):
      """Set up any connections required by the handler
      Should return output of check_connection() method after attempting
      connection. Should switch self.is_connected.
      Returns:
          Connection Object
      """
      if self.is_connected is True:
          return self.connection
  
      url = "http://{0}:{1}@{2}:{3}".format(
          self.user, self.password, self.host, self.port
      )
      try:
          self.connection = db.connect(url)
  
          self.is_connected = True
      except Exception as e:
          logger.error(f"Error while connecting to CrateDB, {e}")
  
      return self.connection
  
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 2 for calling the CrateHandler obj's underlying member method code with example usage: obj.connect() and returns: self, self