code: def test_single_facet(self):
      key = "a"
      order = list("abc")
      spec = {"variables": {"col": key}, "structure": {"col": order}}
      s = Subplots({}, spec, {})
  
      assert s.n_subplots == len(order)
      assert s.subplot_spec["ncols"] == len(order)
      assert s.subplot_spec["nrows"] == 1
      assert s.subplot_spec["sharex"] is True
      assert s.subplot_spec["sharey"] is True
  
imports: import itertools
  import numpy
  import pytest
  from seaborn._core.subplots import Subplots
label_desc: Use image node_id 2 for calling the TestSubplotSpec obj's underlying member method code with example usage: obj.test_single_facet() without return types