code: def test_hashable():
      """
      test that interval objects are hashable.
      this is required in order to be able to put them into the cache, which
      appears to be necessary for plotting in py3k. For details, see:
  
      https://github.com/sympy/sympy/pull/2101
      https://github.com/sympy/sympy/issues/6533
      """
      hash(interval(1, 1))
      hash(interval(1, 1, is_valid=True))
      hash(interval(-4, -0.5))
      hash(interval(-2, -0.5))
      hash(interval(0.25, 8.0))
  
file_path: sympy/sympy/plotting/intervalmath/tests/test_intervalmath.py
imports: from sympy.plotting.intervalmath import interval
  from sympy.testing.pytest import raises
label_desc: Use image node_id 7 for calling a global function with example usage: test_hashable() without return types