'Return a const object if the value is representable as
constant value in the generated code, otherwise it will raise
an `Impossible` exception.'

@classmethod
def from_untrusted(cls, value, lineno=None, environment=None):

    from .compiler import has_safe_repr
    if (not has_safe_repr(value)):
        raise Impossible()
    return cls(value, lineno=lineno, environment=environment)
