code: def test_empty_formatstr(self):
      poly.set_default_printstyle("ascii")
      p = poly.Polynomial([1, 2, 3])
      assert_equal(format(p), "1.0 + 2.0 x + 3.0 x**2")
      assert_equal(f"{p}", "1.0 + 2.0 x + 3.0 x**2")
  
imports: from math import nan, inf
  import pytest
  from numpy._core import array, arange, printoptions
  import numpy.polynomial
  from numpy.testing import assert_equal, assert_
  from fractions import Fraction
  from decimal import Decimal
label_desc: Use image node_id 3 for calling the TestFormat obj's underlying member method code with example usage: obj.test_empty_formatstr() without return types