import numpy as np
a = np.array([[0, 1], [0, 2], [0, 3], [0, 4], [1, 5], [1, 6], [1, 7], [2, 8
    ], [2, 9]])
_, i = np.unique(a[:, (0)], return_index=True)
b = np.delete(a, i, axis=0)
delete the first element in subview of a matrix