parameters: (c1,r1,c2,r2)
return_statement: return math_ad.distance(c1,c2)-r1-r2
docstring: Autodiff function D(c1,r1,c2,r2) giving the distance from a sphere with
      center c1, radius r1 to a sphere with center c2, radius r2.
docstring_summary: Autodiff function D(c1,r1,c2,r2) giving the distance from a sphere with
      center c1, radius r1 to a sphere with center c2, radius r2.
docstring_tokens: Autodiff function D ( c1 r1 c2 r2 ) giving the distance from a sphere with center c1 radius r1 to a sphere with center c2 radius r2 .
function: def sphere_sphere_distance(c1,r1,c2,r2):
      """Autodiff function D(c1,r1,c2,r2) giving the distance from a sphere with
      center c1, radius r1 to a sphere with center c2, radius r2."""
      return math_ad.distance(c1,c2)-r1-r2
function_tokens: def sphere_sphere_distance ( c1 , r1 , c2 , r2 ) : return math_ad . distance ( c1 , c2 ) - r1 - r2