def get_model_pk_column(model_class):
    """
    Get the primary key Column object from a Declarative model class

    :param Type[DeclarativeMeta] model_class: a Declarative class

    :rtype: Column
    """
    primary_keys = model_class.__mapper__.primary_key
    assert len(primary_keys
        ) == 1, 'Nested object must have exactly one primary key'
    return primary_keys[0]
