Efficient iteration.
x.__iter__() <==> iter(x)
Examples
>>> d = cf.Data([1, 2, 3], 'metres')
>>> for e in d:
... print repr(e)
...
1
2
3
>>> d = cf.Data([[1, 2], [4, 5]], 'metres')
>>> for e in d:
... print repr(e)
...
<CF Data: [1, 2] metres>
<CF Data: [4, 5] metres>
>>> d = cf.Data(34, 'metres')
>>> for e in d:
... print repr(e)
..
TypeError: iteration over a 0-d Data