code: def construct_mapping(self, node, deep=False):
          
          mapping = super(ExtendedSafeConstructor, self).construct_mapping(
              node, deep)
  
          return {
              (str(key) if isinstance(key, int) else key): mapping[key]
              for key in mapping
          }
docs: While yaml supports integer keys, these are not valid in
          json, and will break jsonschema. This method coerces all keys
          to strings.