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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_field_errors(self, field):
 """ Return server side errors. Shall be overridden by derived forms to add their extra errors for AngularJS. """

        identifier = format_html('{0}[\'{1}\']', self.form_name, field.name)
        errors = self.errors.get(field.html_name, [])
        return self.error_class([SafeTuple(
            (identifier, self.field_error_css_classes, '$pristine', '$pristine', 'invalid', e)) for e in errors])