'Endianness of the target machine.
The default value is ``\'little\'``, but changes according to :attr:`arch`.
Raises:
AttributeError: An invalid endianness was provided
Examples:
>>> context.clear()
>>> context.endian == \'little\'
True
>>> context.endian = \'big\'
>>> context.endian
\'big\'
>>> context.endian = \'be\'
>>> context.endian == \'big\'
True
>>> context.endian = \'foobar\' #doctest: +ELLIPSIS
Traceback (most recent call last):
AttributeError: endian must be one of [\'be\', \'big\', \'eb\', \'el\', \'le\', \'little\']'

@_validator
def endian(self, endianness):

    endian = endianness.lower()
    if (endian not in ContextType.endiannesses):
        raise AttributeError(('endian    must    be    one    of    %r' % sorted(ContextType.endiannesses)))
    return ContextType.endiannesses[endian]
