code: def merge_vertices(self, digits=None, textured=True):
          
          grouping.merge_vertices(self,
                                  digits=digits,
                                  textured=textured)
docs: If a mesh has vertices that are closer than
          trimesh.constants.tol.merge reindex faces to reference
          the same index for both vertices.
  
          Parameters
          --------------
          digits : int
            If specified overrides tol.merge
          textured : bool
            If True avoids merging vertices with different UV
            coordinates. No effect on untextured meshes.