code: def test__mu1_tetface():
      # Test for out of range acos value sequences.  I'm ashamed to say I found
      # these sequences accidentally in a failing test with random numbers
      _mu1_tetface = intvol._mu1_tetface
      assert_almost_equal(
          _mu1_tetface(1, 0, 0, 10, 10, 0, 0, 20, 20, 40), 0
      )
      assert_almost_equal(
          _mu1_tetface(36, 0, 0, 18, 48, 0, 0, 1, 30, 63), 3
      )
  
imports: from itertools import combinations
  import numpy
  import numpy.linalg
  import pytest
  from numpy.testing import assert_almost_equal, assert_array_equal
  from ..None import intvol
label_desc: Use image node_id 16 for calling a global function with example usage: test__mu1_tetface() without return types