class_docstr: Polygon class for data handling
  
  Parameters
  ----------
  vertices : (Nv, 3) array
      Vertex coordinates. If faces is not specified, then this will instead
      be interpreted as (Nf, 3, 3) array of coordinates.
  edges : (Nv, 2) array
      Constraining edges specified by vertex indices.
  faces : (Nf, 3) array
      Indexes into the vertex array.
  
  Notes
  -----
  All arguments are optional.
docstr: Return an array of vertex indexes representing the convex hull.
  
  If faces have not been computed for this mesh, the function
  computes them.
  If no vertices or faces are specified, the function returns None.
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code: def convex_hull(self):
      """Return an array of vertex indexes representing the convex hull.
  
      If faces have not been computed for this mesh, the function
      computes them.
      If no vertices or faces are specified, the function returns None.
      """
      if self._faces is None:
          if self._vertices is None:
              return None
          self.triangulate()
      return self._convex_hull
  
file_path: vispy/vispy/geometry/polygon.py
imports: import numpy
  from .triangulation import Triangulation
label_desc: Use image node_id 8 for calling the PolygonData obj's underlying member method code with example usage: obj.convex_hull() and returns: self, None