code: function validate(candidate) {
    if (candidate.doc_type) {
      var schema = schemasDeepCopy()[candidate.doc_type];
      validator.validate(candidate, schema);
      var errors = validator.getLastErrors();
      return errors;
    }
  
    return [{
      dataModel: 'the object to be validated is missing a `doc_type` property'
    }];
  }
docs: Thin wrapper to make validation more convenient
  
  @param {Object} candidate A model instance to validate
  @return {[Error]} A list of errors or null