code: public <E> E getFieldValue(ProfileField<E> field) {
          if (field == null) {
              throw new NullPointerException();
          }
  
          String val = mFields.getString(field.getIdentifier());
          return val == null ? null : ProfileFieldConverter.forField(field).fromStorageString(val);
      }
docs: Gets the value of a field from the container
  
  @param field - the field whose value to retrieve
  
  @return the value of the field, or null if the container doesn't have a value for such field