<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _unique_rows_numpy(a):
 """return unique rows"""

    a = np.ascontiguousarray(a)
    unique_a = np.unique(a.view([('', a.dtype)] * a.shape[1]))
    return unique_a.view(a.dtype).reshape((unique_a.shape[0], a.shape[1]))