<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _zscore(a):
 """ Calculating z-score of data on the first axis. If the numbers in any column are all equal, scipy.stats.zscore will return NaN for this column. We shall correct them all to be zeros. Parameters a: numpy array Returns ------- zscore: numpy array The z-scores of input "a", with any columns including non-finite numbers replaced by all zeros. """

    assert a.ndim > 1, 'a must have more than one dimensions'
    zscore = scipy.stats.zscore(a, axis=0)
    zscore[:, np.logical_not(np.all(np.isfinite(zscore), axis=0))] = 0
    return zscore