code: def validate_env(self, envname):
          
          if self.whitelist_envs and envname in self.whitelist_envs:
              return True
          elif self.whitelist_envs:
              return False
  
          if self.blacklist_envs and envname not in self.blacklist_envs:
              return True
          elif self.blacklist_envs:
              # If there is just a True, all envs are blacklisted
              return False
          else:
              return True
docs: Check the name of the environment against the black list and the
          whitelist. If a whitelist is specified only it is checked.