class_docstr: Test IASI L2 reader.
class_docstr_tok: ["Test","IASI","L2","reader","."]
docstr: Test reading emissivity dataset.
  
  Helper function.
docstr_tok: ["Test","reading","emissivity","dataset",".","Helper","function","."]
code: def check_emissivity(self, emis):
      """Test reading emissivity dataset.
  
      Helper function.
      """
      assert np.all(emis == 0.0)
      assert emis.x.size == SCAN_WIDTH
      assert emis.y.size == NUM_SCANLINES
      assert "emissivity_wavenumbers" in emis.attrs
  
imports: import math
  import os
  import unittest
  import numpy
  import pytest
  import xarray
label_desc: Use image node_id 12 for calling the TestIasiL2 obj's underlying member method code with example usage: obj.check_emissivity(emis) without return types