def child(role)
      @cached_children ||= {}
      @cached_children[role.to_sym] ||= self.children.where(:role => role).first || :nil
      @cached_children[role.to_sym] == :nil ? nil : @cached_children[role.to_sym]
    end
def child(role)
      @cached_children ||= {}
      @cached_children[role.to_sym] ||= self.children.where(:role => role).first || :nil
      @cached_children[role.to_sym] == :nil ? nil : @cached_children[role.to_sym]
    end
Return a child process