hardware.systemInfo.serialNumber Returning None

Describe the bug

Get ESXi host object

esxi_obj = content.searchIndex.FindByDnsName(dnsName=esxi_host, vmSearch=False)
if esxi_obj is None:
print(f'ESXi host {esxi_host} not found.')
si.Disconnect()
exit()

Retrieve hardware info from ESXi host

print(dir(esxi_obj.hardware.systemInfo))
hardware_info = esxi_obj.hardware.systemInfo
product_name = hardware_info.model
serial_number = hardware_info.serialNumber

print(f'Product name: {product_name}')
print(f'Serial number: {serial_number}')

Here product name coming properly but serial number coming empty
Product name: XXX System x32 M6 -[1111AC1]-
Serial number: None

Reproduction steps

1.from pyVim.connect import SmartConnect, Disconnect
from pyVmomi import vim

Connect to vCenter or ESXi host

si = SmartConnect(host='your_host', user='your_username', pwd='your_password')

Get the host system object

content = si.RetrieveContent()
host_view = content.viewManager.CreateContainerView(content.rootFolder, [vim.HostSystem], True)
hosts = host_view.view
host = hosts[0] # assuming there is only one ESXi host in the inventory

Get the hardware system info

hardware = host.hardware
system_info = hardware.systemInfo
serial_number = system_info.serialNumber

Disconnect from vCenter or ESXi host

Disconnect(si)

print(f'The serial number of ESXi host {host.name} is {serial_number}.')

Expected behavior

serial number should get proper value but getting None

Additional context

No response

Start with the reported pyVim.connect and vim.HostSystem reproduction, then inspect host.hardware.systemInfo.serialNumber for the affected ESXi or vCenter environment. Compare the returned value with the expected host serial number; done means determining whether the binding can expose the value or documenting an environment-specific limitation.