React eslint not catching the use of underscore with internal methods

In the [React/JSX Styleguide 'Methods' section](https://github.com/airbnb/javascript/blob/master/react/README.md#methods) it says you shouldn't use `_` to prefix internal methods. However, some of my code contains this convention and it isn't being caught by the linter. I double-checked the eslint rules for react/jsx files and there doesn't seem to be a rule defined for this convention.

Is this intentional? If so, why specify the rule in your documentation? I found a related issue (#490), but it wasn't clearly stated whether or not this rule should definitely be adhered to but rather that it's more or less up to the programmer.

Any clarification would be greatly appreciated.

Comienza con la sección «Methods» de React/JSX Styleguide en react/README.md e inspecciona las reglas de ESLint existentes para archivos React/JSX. Revisa el issue #490 relacionado y determina si debe hacerse cumplir la convención documentada del guion bajo; se considera completado cuando se haya decidido una política y se hayan realizado los cambios correspondientes en la documentación o en el linting.

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