11: impl_serde::serialize::to_hex
             at /home/thomas/.cargo/registry/src/github.com-1ecc6299db9ec823/impl-serde-0.2.1/src/serialize.rs:21
  12: impl_serde::serialize::serialize
             at /home/thomas/.cargo/registry/src/github.com-1ecc6299db9ec823/impl-serde-0.2.1/src/serialize.rs:51
  13: <substrate_primitives_storage::_IMPL_SERIALIZE_FOR_StorageKey::<impl serde::ser::Serialize for substrate_primitives_storage::StorageKey>::serialize::__SerializeWith as serde::ser::Serialize>::serialize
             at /home/thomas/.cargo/git/checkouts/substrate-7e08433d4c370a21/acf86cd/core/primitives/storage/src/lib.rs:29
  14: <&mut serde_json::ser::Serializer<W,F> as serde::ser::Serializer>::serialize_newtype_struct
             at /home/thomas/.cargo/registry/src/github.com-1ecc6299db9ec823/serde_json-1.0.41/src/ser.rs:268
  15: substrate_primitives_storage::_IMPL_SERIALIZE_FOR_StorageKey::<impl serde::ser::Serialize for substrate_primitives_storage::StorageKey>::serialize
             at /home/thomas/.cargo/git/checkouts/substrate-7e08433d4c370a21/acf86cd/core/primitives/storage/src/lib.rs:29
  16: serde_json::ser::to_writer
             at /home/thomas/.cargo/registry/src/github.com-1ecc6299db9ec823/serde_json-1.0.41/src/ser.rs:2161
  17: serde_json::ser::to_vec
             at /home/thomas/.cargo/registry/src/github.com-1ecc6299db9ec823/serde_json-1.0.41/src/ser.rs:2195