Test if the attribute given is an internal python attribute.  For
    example this function returns `True` for the `func_code` attribute of
    python objects.  This is useful if the environment method
    :meth:`~SandboxedEnvironment.is_safe_attribute` is overriden.

    >>> from jinja2.sandbox import is_internal_attribute
    >>> is_internal_attribute(lambda: None, "func_code")
    True
    >>> is_internal_attribute((lambda x:x).func_code, 'co_code')
    True
    >>> is_internal_attribute(str, "upper")
    False

def is_internal_attribute(obj, attr):
    """Test if the attribute given is an internal python attribute.  For
    example this function returns `True` for the `func_code` attribute of
    python objects.  This is useful if the environment method
    :meth:`~SandboxedEnvironment.is_safe_attribute` is overriden.

    >>> from jinja2.sandbox import is_internal_attribute
    >>> is_internal_attribute(lambda: None, "func_code")
    True
    >>> is_internal_attribute((lambda x:x).func_code, 'co_code')
    True
    >>> is_internal_attribute(str, "upper")
    False
    """
    if isinstance(obj, FunctionType):
        if attr in UNSAFE_FUNCTION_ATTRIBUTES:
            return True
    elif isinstance(obj, MethodType):
        if attr in UNSAFE_FUNCTION_ATTRIBUTES or \
           attr in UNSAFE_METHOD_ATTRIBUTES:
            return True
    elif isinstance(obj, type):
        if attr == 'mro':
            return True
    elif isinstance(obj, (CodeType, TracebackType, FrameType)):
        return True
    elif isinstance(obj, GeneratorType):
        if attr == 'gi_frame':
            return True
    return attr.startswith('__')