docs: function validateField(fieldId, submission, sectionIndex, cb) {
        init();
  
        if (_.isFunction(sectionIndex)) {
          cb = sectionIndex;
          sectionIndex = 0;
        }
  
        var err = initSubmission(submission);
        if (err) {
          return cb(err);
        }
  
        var submissionField = submissionFieldsMap[fieldId][sectionIndex];
        var fieldDef = fieldMap[fieldId];
  
        getFieldValidationStatus(submissionField, fieldDef, null, function(err, res) {
          if (err) {
            return cb(err);
          }
          var ret = {
            validation: {}
          };
  
          assignValidationResponse(fieldId, sectionIndex, ret.validation, res);
          return cb(undefined, ret);
        });
      }