code: def test_creation():
      x = Symbol("x")
      y = Symbol("y")
      raises(ValueError, lambda: CompanionMatrix(1))
      raises(ValueError, lambda: CompanionMatrix(Poly([1], x)))
      raises(ValueError, lambda: CompanionMatrix(Poly([2, 1], x)))
      raises(ValueError, lambda: CompanionMatrix(Poly(x * y, [x, y])))
      assert unchanged(CompanionMatrix, Poly([1, 2, 3], x))
  
file_path: sympy/sympy/matrices/expressions/tests/test_companion.py
imports: from sympy.core.expr import unchanged
  from sympy.core.symbol import Symbol, symbols
  from sympy.matrices.immutable import ImmutableDenseMatrix
  from sympy.matrices.expressions.companion import CompanionMatrix
  from sympy.polys.polytools import Poly
  from sympy.testing.pytest import raises
label_desc: Use image node_id 1 for calling a global function with example usage: test_creation() without return types