text: foo = 'bar'
  
  assert f"{''}" == ''
  assert f"{f'{foo}'}" == 'bar'
  assert f"foo{foo}" == 'foobar'
  assert f"{foo}foo" == 'barfoo'
  assert f"foo{foo}foo" == 'foobarfoo'
  assert f"{{foo}}" == '{foo}'
  assert f"{ {foo} }" == "{'bar'}"
  assert f"{f'{{}}'}" == '{}' # don't include escaped braces in nested f-strings
  assert f'{f"{{"}' == '{'
  assert f'{f"}}"}' == '}'
  assert f'{foo}' f"{foo}" 'foo' == 'barbarfoo'
  #assert f'{"!:"}' == '!:'
  #assert f"{1 != 2}" == 'True'
  assert fr'x={4*10}\n' == 'x=40\\n'
  assert f'{16:0>+#10x}' == '00000+0x10'
  