创建漂亮表时我看不到表格边框

如何解决创建漂亮表时我看不到表格边框

我正在写这样的简单代码

import prettytable

# open csv file
a = open("dash",'r')

# read the csv file 
a = a.readlines()

# headers for table 
t = prettytable.prettytable(field_names=["Test","Status"],title="Test Report",header_style="title",header=True,hrules=prettytable.ALL,vrules=prettytable.ALL)

# Adding the data 
for i in range(len(a)):
    row = a[i].split(',')
    t.add_row([row[0],row[1]])
    t.add_row(["",""])

code = t.get_html_string()
html_file = open('Table.html','w')
html_file = html_file.write(code)

但是我得到这样的输出

Test Report
Test    Status
test1   pass
test2   fail

为什么我看不到表格边框？