Where to put graphql mutations in Sails?

I've installed npm sails-graphql, but I dont know where to put a mutation, surfing on the web I've found nodejs examples in which they add mutations in index.js but in sails there are no such file. Thanks in advance.

The sails-graphql adapter creates a schema automatically with mutations for all models in /api/models if its specified in the controller:

        // api/controllers/GraphQLController.js
        var graphql = require("graphql");
        var sailsGraphQL = require("sails-graphql");
        ...
        if (!schema) {
        schema = sailsGraphQL.generateSchema(sails.models);
        }
        ...

In this case there is no need to manually add mutations. See https://www.npmjs.com/package/sails-graphql#usage

Although if you want to edit the generated schema, a better option would be to use a graphql implementation for the required language and load the mutations manually.