def gen_call_expr(test_case, prefix):
    """Generate call expression based on method name and parameters and method prefix, e.g. str"""
    prefix_as_list = [prefix] if prefix else []
    call_expr_parts = ['data'] + prefix_as_list + ['{}({})'.format(test_case.name, test_case.params)]

    return '.'.join(call_expr_parts)