code: func (x *Exif) Get(name FieldName) (*tiff.Tag, error) {
  	if tg, ok := x.main[name]; ok {
  		return tg, nil
  	}
  	return nil, TagNotPresentError(name)
  }
docs: // Get retrieves the EXIF tag for the given field name.
  //
  // If the tag is not known or not present, an error is returned. If the
  // tag name is known, the error will be a TagNotPresentError.