def listify(a):
if a is None:<EOL><INDENT>return []<EOL><DEDENT>elif not isinstance(a, (tuple, list, np.ndarray)):<EOL><INDENT>return [a]<EOL><DEDENT>return list(a)<EOL>
Convert a scalar ``a`` to a list and all iterables to list as well.

Examples
--------
>>> listify(0)
[0]

>>> listify([1,2,3])
[1, 2, 3]

>>> listify('a')
['a']

>>> listify(np.array([1,2,3]))
[1, 2, 3]

>>> listify('string')
['string']