tsParseModifier<T: TsModifier>(allowedModifiers: T[]): ?T {
      if (!this.match(tt.name)) {
        return undefined;
      }

      const modifier = this.state.value;
      if (
        allowedModifiers.indexOf(modifier) !== -1 &&
        this.tsTryParse(this.tsNextTokenCanFollowModifier.bind(this))
      ) {
        return modifier;
      }
      return undefined;
    }
Parses a modifier matching one the given modifier names.