Numpy has no unsqueeze function

unsqueeze： Add a length of 1 Dimensions .

import torch
arr = torch.Tensor(3, 5)
# print(type(arr), arr, arr.shape, sep='\n')  #torch.Size([3, 5])
arr_1 = arr.unsqueeze(0) #torch.Size([1, 3, 5]) ###‘ Add dimension to the head ’
# print(type(arr_1), arr_1, arr_1.shape, sep='\n')
arr_2 = arr.unsqueeze(-1) #torch.Size([3, 5, 1])  ###‘ Tail plus dimension ’
# print(type(arr_2), arr_2, arr_2.shape, sep='\n')
arr_3 = arr.unsqueeze(1)#torch.Size([3, 1, 5])   ###‘ Add dimension in the middle ’
# print(type(arr_3), arr_3, arr_3.shape, sep='\n')
arr_4 = arr.unsqueeze(2)        #  No matter how big the number is, it will be wrong   #torch.Size([3, 5, 1])  and “##（-1） equally 
print(type(arr_4), arr_4, arr_4.shape, sep='\n')