<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def mean(x):
 """ Return a numpy array of column mean. It does not affect if the array is one dimension Parameters x : ndarray A numpy array instance Returns ------- ndarray A 1 x n numpy array instance of column mean Examples -------- True True """

    if x.ndim > 1 and len(x[0]) > 1:
        return np.mean(x, axis=1)
    return x