This is my object, we'll call it "some_hash":
{
"object1": {["key1.1","key1.2"]=>["1","2","3"],["key2.1","key2.2"]=>["1","2","3"],["key3.1","key3.2"]=>["1","2","3"]}
"object2": [["1","2","3"],["1","2","3"],["1","2","3"]]
}

And:
some_hash["object1"].keys
Gives:
[["key1.1", "key1.2"], ["key2.1", "key2.2"], ["key3.1", "key3.2"]]

However:
JSON.parse(JSON.generate(some_hash))["object1"].keys
Gives:
["[\"key1.1\", \"key1.2\"]", "[\"key2.1\", \"key2.2\"]", "[\"key3.1\", \"key3.2\"]"]

The keys are now strings instead of arrays.