code: def _check_dep(self, depinfo, deptile, resolver):
          
  
          try:
              settings = self._load_depsettings(deptile)
          except IOError:
              return False
  
          # If this dependency was initially resolved with a different resolver, then
          # we cannot check if it is up to date
          if settings['resolver'] != resolver.__class__.__name__:
              return None
  
          resolver_settings = {}
          if 'settings' in settings:
              resolver_settings = settings['settings']
  
          return resolver.check(depinfo, deptile, resolver_settings)
docs: Check if a dependency tile is up to date
  
          Returns:
              bool: True if it is up to date, False if it not and None if this resolver
                  cannot assess whether or not it is up to date.