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.
The arch of the newborn's foot is covered with a fat pad, giving the foot the appearance of being flat. Newborns and infants have fat pads where the arch should be; the arch develops when the toddler begins to walk. Flat feet are no more common in children than in adults. The size of the feet is not relevant.