method
    
    include?
  include?(o)
  public
  Returns true if the set contains the given object.
Note that include? and member? do not test member equality using == as do other Enumerables.
See also Enumerable#include?
  include?(o)
  public
  Returns true if the set contains the given object.
Note that include? and member? do not test member equality using == as do other Enumerables.
See also Enumerable#include?