Returns the data element registry for the given content type (a Singleton).

    :Note: This only works after a representer for the given content type
        has been created.

def get_mapping_registry(content_type):
    """
    Returns the data element registry for the given content type (a Singleton).

    :Note: This only works after a representer for the given content type
        has been created.
    """
    reg = get_current_registry()
    rpr_reg = reg.queryUtility(IRepresenterRegistry)
    return rpr_reg.get_mapping_registry(content_type)