class TakisField(forms.CharField):

    def validate(self, value):
        import json
        try:
            s = json.dumps("{}".format(value))
            j = json.loads(s)
        except:
            raise forms.ValidationError("Invalid StructuredValue field. Not a valid JSON")

    def to_python(self, value):
        import json
        try:
            new_value = json.loads(value)
        except:
            raise forms.ValidationError("Invalid StructuredValue field. Not a valid JSON")
        else:
            return new_value