(triangles, fringe, grid)
return None
Finds, if possible, a triangle and an edge in the fringe to
        which the triangle could be attached.  Returns the tuple
        containing the triangle and the index of the corresponding
        edge in the fringe.

        This function relies on the fact that objects are unique in
        the diagram.
Finds, if possible, a triangle and an edge in the fringe to
        which the triangle could be attached.  Returns the tuple
        containing the triangle and the index of the corresponding
        edge in the fringe.
Finds if possible a triangle and an edge in the fringe to which the triangle could be attached . Returns the tuple containing the triangle and the index of the corresponding edge in the fringe .
def _find_triangle_to_weld(triangles, fringe, grid):
        """
        Finds, if possible, a triangle and an edge in the fringe to
        which the triangle could be attached.  Returns the tuple
        containing the triangle and the index of the corresponding
        edge in the fringe.

        This function relies on the fact that objects are unique in
        the diagram.
        """
        for triangle in triangles:
            for (a, b) in fringe:
                if frozenset([grid[a], grid[b]]) in triangle:
                    return (triangle, (a, b))
        return None
def _find_triangle_to_weld ( triangles , fringe , grid ) : for triangle in triangles : for ( a , b ) in fringe : if frozenset ( [ grid [ a ] , grid [ b ] ] ) in triangle : return ( triangle , ( a , b ) ) return None