code: def test_is_single_string_selector() -> None:
      assert q.is_single_string_selector(dict(foo="c"), "foo")
      assert not q.is_single_string_selector(
          dict(foo="c", bar="d"), "foo"
      )
      assert not q.is_single_string_selector(dict(foo=42), "foo")
  
file_path: bokeh/tests/unit/bokeh/core/test_query.py
imports: from __future__ import annotations
  import pytest
  from bokeh.models import Axis, BoxZoomTool, ColumnDataSource, DatetimeAxis, Glyph, GlyphRenderer, Grid, Line, LinearAxis, LogAxis, PanTool, Plot, Range1d, Rect, ResetTool, SaveTool, Scatter, Tool, WheelZoomTool
  import bokeh.core.query
label_desc: Use image node_id 12 for calling a global function with example usage: test_is_single_string_selector() without return types