"def ismember()" The actual function is different from the meaning of the name. why???

[BingYu94860]

preprocessing.py -> def mask_test_edges(adj): -> def ismember(a, b, tol=5):

The actual function is different from the meaning of the name. why???

Actual function： is same rows (https://www.coder.work/article/2401015)
Surface name function： is member

import numpy as np

def ismember(a, b, tol=5):
  rows_close = np.all(np.round(a - b[:, None], tol) == 0, axis=-1)
  return (np.all(np.any(rows_close, axis=-1), axis=-1) and np.all(np.any(rows_close, axis=0), axis=0))

#[is same rows]
a = np.array([[ 6,  7],
              [ 2,  3],
              [ 0,  1],
              [ 4,  5],
              [ 8,  9]])
b = np.array([[ 0,  1],
              [ 2,  3],
              [ 4,  5],
              [ 6,  7],
              [ 8,  9]])
print(ismember(a, b)) 
# >> True

#[is member]
a1 = np.array([[ 0,  1]]) # shape=(1, 2)
print(ismember(a1, b)) 
# >> False # error

a2 = np.array([ 0,  1]) # shape=(2,)
print(ismember(a2, b)) 
# >> False # error