docstr: Draw a horizontal line on the axis
code: def draw_annotation(self, axis, position, opts):
      "Draw a horizontal line on the axis"
      gradient, intercept = position
      if self.invert_axes:
          if gradient == 0:
              gradient = np.inf, np.inf
          else:
              gradient, intercept = 1 / gradient, -(
                  intercept / gradient
              )
      artist = ABLine2D(*position, axes=axis, **opts)
      return [artist]
  
imports: import matplotlib
  import numpy
  import pandas
  import param
  from matplotlib import patches
  from matplotlib.lines import Line2D
  from ...core.options import abbreviated_exception
  from ...core.util import match_spec
  from ...element import HLines, HSpans, VLines, VSpans
  from .element import ColorbarPlot, ElementPlot
  from .plot import mpl_rc_context
label_desc: Use image node_id 1 for calling the SlopePlot obj's underlying member method code with example usage: obj.draw_annotation(axis, position, opts) and returns: list