How to get class constant name in ruby

I need get constant name from this:

class Sex
    Male = 1
    Female = 2
end

But this is perfect variant, can i get constant name at least from this:

class Sex
    self.Male = 1
    self.Female = 2
end

Few details about the problem:

• You can get a list of methods: Class.methods - Object.methods
• You can get a list of instance variables: instance_variables.map{|ivar| instance_variable_get ivar}
• You can get a list of constant names from Module: Module.constants

But i have no idea how I can get class constant names.