code: def test_StrCategoryFormatter(self, ydata):
      unit = cat.UnitData(ydata)
      labels = cat.StrCategoryFormatter(unit._mapping)
      for i, d in enumerate(ydata):
          assert labels(i, i) == d
          assert labels(i, None) == d
  
imports: import warnings
  import pytest
  import numpy
  import matplotlib
  from matplotlib.axes import Axes
  import matplotlib.pyplot
  import matplotlib.category
  from matplotlib.testing.decorators import check_figures_equal
label_desc: Use image node_id 1 for calling the TestStrCategoryFormatter obj's underlying member method code with example usage: obj.test_StrCategoryFormatter(ydata) without return types