Return second Schema, which is extended by first Schema
        https://github.com/OAI/OpenAPI-Specification/blob/master/versions/2.0.md#composition-and-inheritance-polymorphism

def merge_schemas(cls, schema, _schema):
        """Return second Schema, which is extended by first Schema
        https://github.com/OAI/OpenAPI-Specification/blob/master/versions/2.0.md#composition-and-inheritance-polymorphism
        """
        tmp = schema.properties[:]  # copy
        prop = {}
        to_dict = lambda e: prop.update({e.pop('name'): e})
        [to_dict(i) for i in tmp]  # map(to_dict, tmp)
        for _prop in _schema.properties:
            if prop.get(_prop['name']):
                prop.pop(_prop['name'])
        if prop:
            for k, v in prop.items():
                v['name'] = k
                _schema.properties.append(v)
        return _schema