overrides not working properly for load_hyperpyyaml with !include

[weiwei-ww]

Suppose that I have the following two YAML files:

f1.yaml:

k1: v1
k2: !include:f2.yaml

f2.yaml

k3: v3

With no overrides, after calling load_hyperpyyaml, we should get {k1: v1, k2: {k3: v3}}.

When load_hyperpyyaml is called with overrides={k1: new_v1}, the expected result should be {k1: new_v1, k2: {k3: v3}} (i.e. with v1 replaced by new_v1). However, the actual result is {k1: new_v1, k2: {k3: v3, k1: new_v1}}, with an additional unexpected key inserted to k2.