Covert json to schema fileds with camel casing

Question

I have a json:

[{
"myKey": "key"
}]

My schema is:

_snake_case = re.compile(r"(?<=\w)_(\w)")
_to_camel_case = partial(_snake_case.sub, lambda m: m[1].upper())

class CamelCasedSchema(Schema):
    """Gives fields a camelCased data key"""
    def on_bind_field(self, field_name, field_obj, _cc=_to_camel_case):
        field_obj.data_key = _cc(field_name.lower())

class KeySchema(CamelCasedSchema):
    my_key = fields.String(required=True, data_key="myKey")

I am loading it as:

KeySchema(many=True).load(json)

I want that the json [{ "myKey": "key" }] gets converted to schema and i can get my_key as key.

Right now i am getting:

Original Error {0: {'my_key': ['Missing data for required field.']}}

What am i missing here?

marshmallow version is 3.0.0rc1