devices silently dropped when outputting in tree mode

[furlongm]

pcicrawler -t displays nothing when all devices are root devices (e.g. when running on a VM as below):

# pcicrawler -t
#

Adding some print statement, I can see the devices are there, but are silently skipped:

# pcicrawler -t
<PCIDevice vendor_id=0x8086 device_id=0x1237 class_id=0x60000 domain_id=0x0000 bus_id=0x0000 bus_device_id=0x0000 device_function_id=0x0000>
<PCIDevice vendor_id=0x8086 device_id=0x7000 class_id=0x60100 domain_id=0x0000 bus_id=0x0000 bus_device_id=0x0001 device_function_id=0x0000>
<PCIDevice vendor_id=0x8086 device_id=0x7010 class_id=0x10180 domain_id=0x0000 bus_id=0x0000 bus_device_id=0x0001 device_function_id=0x0001>
<PCIDevice vendor_id=0x8086 device_id=0x7020 class_id=0xc0300 domain_id=0x0000 bus_id=0x0000 bus_device_id=0x0001 device_function_id=0x0002>
<PCIDevice vendor_id=0x8086 device_id=0x7113 class_id=0x68000 domain_id=0x0000 bus_id=0x0000 bus_device_id=0x0001 device_function_id=0x0003>
<PCIDevice vendor_id=0x1013 device_id=0x00B8 class_id=0x30000 domain_id=0x0000 bus_id=0x0000 bus_device_id=0x0002 device_function_id=0x0000>
<PCIDevice vendor_id=0x1AF4 device_id=0x1000 class_id=0x20000 domain_id=0x0000 bus_id=0x0000 bus_device_id=0x0003 device_function_id=0x0000>
<PCIDevice vendor_id=0x1AF4 device_id=0x1001 class_id=0x10000 domain_id=0x0000 bus_id=0x0000 bus_device_id=0x0004 device_function_id=0x0000>
<PCIDevice vendor_id=0x1AF4 device_id=0x1002 class_id=0xff00 domain_id=0x0000 bus_id=0x0000 bus_device_id=0x0005 device_function_id=0x0000>

Would it be possible to display these devices in tree mode?

Compare to e.g. the output of lspci in tree mode:

# lspci -t -vv
-[0000:00]-+-00.0  Intel Corporation 440FX - 82441FX PMC [Natoma]
           +-01.0  Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II]
           +-01.1  Intel Corporation 82371SB PIIX3 IDE [Natoma/Triton II]
           +-01.2  Intel Corporation 82371SB PIIX3 USB [Natoma/Triton II]
           +-01.3  Intel Corporation 82371AB/EB/MB PIIX4 ACPI
           +-02.0  Cirrus Logic GD 5446
           +-03.0  Red Hat, Inc. Virtio network device
           +-04.0  Red Hat, Inc. Virtio block device
           \-05.0  Red Hat, Inc. Virtio memory balloon

or to the output of pcicrawler without tree mode:

# pcicrawler
0000:00:04.0, Red Hat, Inc. (1af4) Virtio block device (1001)
0000:00:05.0, Red Hat, Inc. (1af4) Virtio memory balloon (1002)
0000:00:01.1, Intel Corporation (8086) 82371SB PIIX3 IDE [Natoma/Triton II] (7010)
0000:00:01.3, Intel Corporation (8086) 82371AB/EB/MB PIIX4 ACPI (7113)
0000:00:02.0, Cirrus Logic (1013) GD 5446 (00b8)
0000:00:03.0, Red Hat, Inc. (1af4) Virtio network device (1000)
0000:00:01.2, Intel Corporation (8086) 82371SB PIIX3 USB [Natoma/Triton II] (7020)
0000:00:01.0, Intel Corporation (8086) 82371SB PIIX3 ISA [Natoma/Triton II] (7000)
0000:00:00.0, Intel Corporation (8086) 440FX - 82441FX PMC [Natoma] (1237)