code: def is_colliding(self, other):
          
          if isinstance(other, BoundingCircle):
              #Calculate the distance between two circles.
              distance = Vector2.distance(self.coords, other.coords)
  
              #Check to see if the sum of thier radi are greater than or equal to the distance.
              radi_sum = self.radius + other.radius
  
              if distance <= radi_sum:
                  #There has been a collision
  ##                print "Distance: ", distance, "\nRadi Sum: ", radi_sum
  ##                print "Self Coords: ", self.coords, "\nOther Coords: ", other.coords
                  return True
  
              #No collision.
              return False
docs: Check to see if two circles are colliding.