code: def triplot(ax, *args, **kwargs):
      """
      Draw an unstructured triangular grid as lines and/or markers.
  
      Call signatures::
  
        triplot(triangulation, ...)
        triplot(x, y, [triangles], *, [mask=mask], ...)
  
      The triangular grid can be specified either by passing a `.Triangulation`
      object as the first parameter, or by passing the points *x*, *y* and
      optionally the *triangles* and a *mask*. If neither of *triangulation* or
      *triangles* are given, the triangulation is calculated on the fly.
  
      Parameters
      ----------
      triangulation : `.Triangulation`
          An already created triangular grid.
      x, y, triangles, mask
          Parameters defining the triangular grid. See `.Triangulation`.
          This is mutually exclusive with specifying *triangulation*.
      other_parameters
          All other args and kwargs are forwarded to `~.Axes.plot`.
  
      Returns
      -------
      lines : `~matplotlib.lines.Line2D`
          The drawn triangles edges.
      markers : `~matplotlib.lines.Line2D`
          The drawn marker nodes.
      """
      import matplotlib.axes
  
      tri, args, kwargs = Triangulation.get_from_args_and_kwargs(
          *args, **kwargs
      )
      x, y, edges = (tri.x, tri.y, tri.edges)
  
      # Decode plot format string, e.g., 'ro-'
      fmt = args[0] if args else ""
      (
          linestyle,
          marker,
          color,
      ) = matplotlib.axes._base._process_plot_format(fmt)
  
      # Insert plot format string into a copy of kwargs (kwargs values prevail).
      kw = cbook.normalize_kwargs(kwargs, mlines.Line2D)
      for key, val in zip(
          ("linestyle", "marker", "color"), (linestyle, marker, color)
      ):
          if val is not None:
              kw.setdefault(key, val)
  
      # Draw lines without markers.
      # Note 1: If we drew markers here, most markers would be drawn more than
      #         once as they belong to several edges.
      # Note 2: We insert nan values in the flattened edges arrays rather than
      #         plotting directly (triang.x[edges].T, triang.y[edges].T)
      #         as it considerably speeds-up code execution.
      linestyle = kw["linestyle"]
      kw_lines = {
          **kw,
          "marker": "None",  # No marker to draw.
          "zorder": kw.get("zorder", 1),  # Path default zorder is used.
      }
      if linestyle not in [None, "None", "", " "]:
          tri_lines_x = np.insert(x[edges], 2, np.nan, axis=1)
          tri_lines_y = np.insert(y[edges], 2, np.nan, axis=1)
          tri_lines = ax.plot(
              tri_lines_x.ravel(), tri_lines_y.ravel(), **kw_lines
          )
      else:
          tri_lines = ax.plot([], [], **kw_lines)
  
      # Draw markers separately.
      marker = kw["marker"]
      kw_markers = {
          **kw,
          "linestyle": "None",  # No line to draw.
      }
      kw_markers.pop("label", None)
      if marker not in [None, "None", "", " "]:
          tri_markers = ax.plot(x, y, **kw_markers)
      else:
          tri_markers = ax.plot([], [], **kw_markers)
  
      return tri_lines + tri_markers
  
imports: import numpy
  from matplotlib.tri._triangulation import Triangulation
  import matplotlib.cbook
  import matplotlib.lines
label_desc: Use image node_id 1 for calling a global function with example usage: triplot(ax) and returns: unknown