code: def test_fstring_with_vars_missing():
      fstring = FString(
          template="{greeting}, {name}!", variables=["name"]
      )
      with pytest.raises(KeyError):
          fstring.run(greeting="Hello")
  
imports: import pytest
  from haystack.testing.sample_components import FString
label_desc: Use image node_id 6 for calling a global function with example usage: test_fstring_with_vars_missing() without return types