code: def _checkValidClusterName(self):
          
          p = re.compile('^[a-zA-Z0-9][a-zA-Z0-9_.\-]*[a-zA-Z0-9]$')
          if len(self.clusterName) < 2 or len(self.clusterName) > 64 or not p.match(self.clusterName):
              raise RuntimeError("Invalid cluster name (%s)."
                                  " It must be between 2 and 64 characters and contain only alpha-numeric"
                                  " characters, hyphens, underscores, and periods. It must start and"
                                  " end only with alpha-numeric characters." % self.clusterName)
docs: Cluster names are used for resource groups, security groups, virtual networks and subnets, and
          therefore, need to adhere to the naming requirements for each:
          * Between 2 and 64 characters
          * Using alphanumeric characters, underscores, hyphens, or periods.
          * Starts and ends with an alphanumeric character.
          More info on naming conventions:
          https://docs.microsoft.com/en-us/azure/architecture/best-practices/naming-conventions