```ruby
# Copyright (C) 2015  Ruby-GNOME2 Project Team
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

module Gtk
  class IconTheme
    def icons(context=nil)
      list_icons(context)
    end

    alias_method :choose_icon_raw, :choose_icon
    def choose_icon(icon_name, size, flags=nil)
      if flags.nil?
        flags = :generic_fallback
      end
      choose_icon_raw(icon_name, size, flags)
    end

    def contexts
      list_contexts
    end
  end
end
```

Use alias_method instead of method define
user
```ruby
# Copyright (C) 2015  Ruby-GNOME2 Project Team
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

module Gtk
  class IconTheme
    alias_method :icons, :list_icons
    alias_method :contexts, :list_contexts

    alias_method :choose_icon_raw, :choose_icon
    def choose_icon(icon_name, size, flags=nil)
      if flags.nil?
        flags = :generic_fallback
      end
      choose_icon_raw(icon_name, size, flags)
    end
  end
end
```
assistant