code: def test_safe_format_safety(self):
      env = SandboxedEnvironment()
      t = env.from_string(
          '{{ ("a{0.__class__}b{1}"|safe).format(42, "<foo>") }}'
      )
      assert t.render() == "ab&lt;foo&gt;"
  
imports: import pytest
  from jinja2 import Environment
  from jinja2 import escape
  from jinja2 import Markup
  from jinja2._compat import text_type
  from jinja2.exceptions import SecurityError
  from jinja2.exceptions import TemplateRuntimeError
  from jinja2.exceptions import TemplateSyntaxError
  from jinja2.nodes import EvalContext
  from jinja2.sandbox import ImmutableSandboxedEnvironment
  from jinja2.sandbox import SandboxedEnvironment
  from jinja2.sandbox import unsafe
label_desc: Use image node_id 3 for calling the TestStringFormat obj's underlying member method code with example usage: obj.test_safe_format_safety() without return types