code: def test_regular_formula():
      f1 = bmb.Formula("y ~ x1 + x2")
      assert f1.main == "y ~ x1 + x2"
      assert f1.additionals == tuple()
      assert f1.additionals_lhs == list()
  
file_path: bambi/tests/test_formula.py
imports: import pytest
  import bambi
label_desc: Use image node_id 1 for calling a global function with example usage: test_regular_formula() without return types