code: def do_check(self, params):
          
          if not self.in_transaction:
              return
  
          self.client_context.check(params.path, params.version)
docs: \x1b[1mNAME\x1b[0m
          check - Checks that a path is at a given version (only works within a transaction)
  
  \x1b[1mSYNOPSIS\x1b[0m
          check <path> <version>
  
  \x1b[1mEXAMPLES\x1b[0m
          > txn 'create /foo "start"' 'check /foo 0' 'set /foo "end"' 'rm /foo 1'