code: def test_Slope() -> None:
      slope = Slope()
      assert slope.gradient is None
      assert slope.y_intercept is None
      assert slope.x_range_name == "default"
      assert slope.y_range_name == "default"
      assert slope.level == "annotation"
      check_line_properties(slope, "", "black", 1.0)
      check_properties_existence(
          slope,
          [
              *ANNOTATION,
              "gradient",
              "y_intercept",
          ],
          LINE,
          ABOVE_FILL,
          ABOVE_HATCH,
          BELOW_FILL,
          BELOW_HATCH,
      )
  
imports: from __future__ import annotations
  import pytest
  from datetime import datetime
  from unittest import mock
  from bokeh.core.properties import field, value
  from bokeh.core.validation import check_integrity, process_validation_issues
  from bokeh.models import Arrow, ArrowHead, Band, BoxAnnotation, ColorBar, ColumnDataSource, GlyphRenderer, Label, LabelSet, Legend, LegendItem, LinearColorMapper, Node, PolyAnnotation, Slope, Span, Title, Whisker
  from bokeh.util.serialization import convert_datetime_type
  from _util_models import ABOVE_FILL, ABOVE_HATCH, ANGLE, BELOW_FILL, BELOW_HATCH, FILL, HATCH, HOVER_FILL, HOVER_HATCH, HOVER_LINE, LINE, TEXT, check_fill_properties, check_hatch_properties, check_line_properties, check_properties_existence, check_text_properties, prefix
label_desc: Use image node_id 13 for calling a global function with example usage: test_Slope() without return types