old_contents: import re
  from django.core.validators import RegexValidator
  from django.forms.fields import Field
  from django.forms.widgets import Input
  from django.utils.translation import ugettext as _
  
  
  class CommaSeparatedEmailField(Field):
      default_validators = [RegexValidator(
          # a list of emails, separated by commas with optional space after
          regex=r'^([^@]+@[^@\s]+\.[^@\s,]+((,\s?)|$))+$',
          message=_('Please enter correct e-mail addresses, separated by '
                    'commas.')
      )]
  
      widget = Input(attrs={
          'placeholder': 'maria@beispiel.de, peter@beispiel.de, '
                         'nicola@beispiel.de,…'
      })
  
      def to_python(self, value):
          emails_str = value.strip(' ,')
          return re.split(r',\s?', emails_str)
  
new_contents: import re
  from django.core.validators import RegexValidator
  from django.forms.fields import Field
  from django.forms.widgets import Input
  from django.utils.translation import ugettext as _
  
  
  class CommaSeparatedEmailField(Field):
      default_validators = [RegexValidator(
          # a list of emails, separated by commas with optional space after
          regex=r'^([^@]+@[^@\s]+\.[^@\s,]+((,\s?)|$))+$',
          message=_('Please enter correct e-mail addresses, separated by '
                    'commas.')
      )]
  
      widget = Input(attrs={
          'placeholder': 'maria@example.com, peter@example.com, '
                         'nicola@example.com,…'
      })
  
      def to_python(self, value):
          emails_str = value.strip(' ,')
          return re.split(r',\s?', emails_str)
  
subject: update placeholder