'Returns a string representation of the allowed values for
printing purposes
Returns:
str: representation of the allowed values'

@property
def allowed_values(self):

    if (self.values is not None):
        v = tuple((str(x) for x in self.values))
        return ',    '.join(v)
    docstring = inspect.getdoc(self.single_value_validator)
    v = (docstring if docstring else '')
    return v
