old_contents: from wtforms import ValidationError
  
  
  def validate_numeric(form, field):
      try:
          int(field.data)
      except ValueError:
          raise ValidationError('Value is not numeric.')
  
new_contents: from wtforms import ValidationError
  
  
  def numeric(form, field):
      try:
          int(field.data)
      except ValueError:
          raise ValidationError('Value is not numeric.')
  
subject: rename numeric validator