docs: function setUnits (form, fieldGroup) {
      var hasUnit = false
      var noUnit = false
      // check all fields in group to see if they have unit field
      _.each(fieldGroup, field => {
          if (field.unit) {
              hasUnit = true
          }
          else {
              noUnit = true
          }
      })
      // if some fields have unit property and other dont throw error
      assert.ok(!(hasUnit && noUnit), 'some fields do not have unit')
      // if unit already defined do nothing
      if (hasUnit) {
          return
      }
      // 
      var units = fieldGroup.length
      // add unit property to each
      _.each(fieldGroup, field => {
          field.unit = '1-'+units
      })
  }