code: function(options) {
      options = options || {}
      const definition = this.definition
      const graphqlHelper = definition.graphqlHelper || { fields: {} }
      const exclude = options.exclude || graphqlHelper.exclude || []
      const result = []
      const customDone = {}
  
      options.description = options.description || graphqlHelper.description
  
      if (options.description) result.push('# ' + options.description)
      result.push('type ' + (options.name || definition.modelName) + ' {')
  
      Object.keys(definition.attributes)
        .sort()
        .forEach(function(key) {
          var attribute = definition.attributes[key]
          if (attribute.hidden) return // hidden fields are for example auto generated `<relation>_ids` fields
          if (exclude.indexOf(key) !== -1) return
          if (!attribute.type.graphQLTypeName) return // auto generated graphql type via openrecord type
          if (graphqlHelper.fields[key]) {
            // field overwrite via this.graphQLField('field definition...')
            result.push('  ' + graphqlHelper.fields[key])
            customDone[key] = true
            return
          }
  
          var attr = ['  ']
          attr.push(key)
          attr.push(': ')
          attr.push(attribute.type.graphQLTypeName)
          if (attribute.notnull) attr.push('!')
          if (attribute.comment) attr.push(' # ' + attribute.comment)
  
          result.push(attr.join(''))
        })
  
      Object.keys(graphqlHelper.fields).forEach(function(key) {
        if (customDone[key]) return
        result.push('  ' + graphqlHelper.fields[key])
      })
  
      result.push('}')
  
      return result.join('\n')
    }
docs: returns a string represing the model as a graphql type
  @param  {Object} options Optional options
  @param  {String} options.name Overwrite the type name (Default: Model name)
  @param  {String} options.description Set a description for the type
  @param  {Array} options.exclude Array of fields to exclude
  @return {String}         The graphql type