| source, want[, exc_msg][, lineno][, indent][, options]) | 
Example defines the following member variables. They are initialized by the constructor, and should not be modified directly.
None if it is not
    expected to generate an exception.  This exception message is
    compared against the return value of
    traceback.format_exception_only().  exc_msg
    ends with a newline unless it's None.  The constructor adds
    a newline if needed.
True or
    False, which is used to override default options for this
    example.  Any option flags not contained in this dictionary are
    left at their default value (as specified by the
    DocTestRunner's optionflags).
    By default, no options are set.
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