Dump fails with UserDict

[acetylen]

• Python version: 3.7.3
• toml version: 0.10.0

It seems like UserDict and subclasses thereof are interpreted as objects and skipped by the dumper when they occur below the top-level of an input dictionary.

test.toml:

global_key = "test"

[category]
name = "foo"
index = 75

[category.thing]
item = "thing"
value = 36.3

[category.device]
item = "device"
keys = 8

Test:

from collections import UserDict

import toml

a = toml.load("test.toml")
b = toml.load("test.toml", _dict=UserDict)

ad = toml.dumps(a)
bd = toml.dumps(b)

print(f'{type(a).__name__}:\n"""\n{ad}"""')
print("-" * 50)
print(f'{type(b).__name__}:\n"""\n{bd}"""')

Output:

dict:
"""
global_key = "test"

[category]
name = "foo"
index = 75

[category.thing]
item = "thing"
value = 36.3

[category.device]
item = "device"
keys = 8
"""
--------------------------------------------------
UserDict:
"""
global_key = "test"
category = [ "name", "index", "thing", "device",]
"""