def get_source(example):
    """
    Return the source with the leading 'sage: ' stripped off.

    EXAMPLES::

        sage: from sage.doctest.parsing import get_source
        sage: from sage.doctest.sources import DictAsObject
        sage: example = DictAsObject({})
        sage: example.sage_source = "2 + 2"
        sage: example.source = "sage: 2 + 2"
        sage: get_source(example)
        '2 + 2'
        sage: example = DictAsObject({})
        sage: example.source = "3 + 3"
        sage: get_source(example)
        '3 + 3'
    """
    return getattr(example, 'sage_source', example.source)