def check_1d(inp):
if isinstance(inp, list):<EOL><INDENT>return check_1d(np.array(inp))<EOL><DEDENT>if isinstance(inp, np.ndarray):<EOL><INDENT>if inp.ndim == <NUM_LIT:1>: <EOL><INDENT>return inp<EOL><DEDENT><DEDENT>
Check input to be a vector. Converts lists to np.ndarray.

Parameters
----------
inp : obj
    Input vector

Returns
-------
numpy.ndarray or None
    Input vector or None

Examples
--------
>>> check_1d([0, 1, 2, 3])
[0, 1, 2, 3]

>>> check_1d('test')
None