Any function object that is a class attribute defines a method for instances of that class. It is not necessary that the function definition is textually enclosed in the class definition: assigning a function object to a local variable in the class is also ok.
Most children are born with very little arch in the feet. As they grow and walk, the soft tissues along the bottom of the feet tighten, which gradually shapes the arches of the feet. Children with flexible flatfoot often do not begin to develop an arch until the age of 5 years or older. Some children never develop an arch. If flexible flatfoot continues into adolescence, a child may experience aching pain along the bottom of the foot. A doctor should be consulted if a child's flatfeet cause pain.
A child at age 3 years (left) with flexible flatfoot. The same child at age 15 years (right) has a normal arch despite having received no treatment. (Reproduced with permission from Sullivan JA: Pedatric Flatfoot: Evaluation and Management.