How to configure __init__ in FlaskForm to have same functionalities?

def __init__(self, username, *args, **kwargs):
    super(SongForm, self).__init__(*args, **kwargs)
    self.album = SelectField("Album", choices=Album.get_albums(username), validate_choice=True )
    self.album.label = 'Album' # here is your error
name = StringField("Name", validators=[DataRequired(),Length(max=40)])
# within the form class
self.album.label = Label(, 'Album Name')

# or on a form instance
form2.album.label = Label(, 'Album Name')
class SongForm(FlaskForm):
    name = StringField("Name", validators=[DataRequired(),Length(max=40)])
    cover = StringField("Cover", validators=[DataRequired(),Length(max=120)])
    content = StringField("Content", validators=[DataRequired(),Length(max=120)])
    release_date = DateField("Release Date", validators=[DataRequired()])
    genre = SelectField("Genre")
    album = SelectField("Album", validate_choice=True)

@artist.route('/insertsong', methods=['GET','POST'])
def insertsong():
    form = ModifyProfileForm() # <-- don't mind this form will be removed later
    form2 = SongForm()
    # Set your choices at runtime
    form2.genre.choices = Genre.list
    form2.album.choices = Album.get_albums(username)
    return render_template('insertsong.html', form = form, form2=form2, user = current_user)