def remove(self, elem):
        """Remove a requirement.

        :param elem: a string or :class:`Requirement` instance.
        """
        if isinstance(elem, text_type):
            for requirement in self:
                if requirement.package == elem:
                    return super(Requirements, self).remove(requirement)
        return super(Requirements, self).remove(elem)
def draw(self, context):
        layout = self.layout

        layout.operator(
                "wm.url_open", text="Add-ons Catalog", icon='URL',
                ).url = "http://wiki.blender.org/index.php/Extensions:2.6/Py/Scripts"

        layout.separator()

        layout.operator(
                "wm.url_open", text="How to share your add-on", icon='URL',
                ).url = "http://wiki.blender.org/index.php/Dev:Py/Sharing"
        layout.operator(
                "wm.url_open", text="Add-on Guidelines", icon='URL',
                ).url = "http://wiki.blender.org/index.php/Dev:2.5/Py/Scripts/Guidelines/Addons"
        layout.operator(
                "wm.url_open", text="API Concepts", icon='URL',
                ).url = bpy.types.WM_OT_doc_view._prefix + "/info_quickstart.html"
        layout.operator("wm.url_open", text="Add-on Tutorial", icon='URL',
                ).url = "http://www.blender.org/api/blender_python_api_current/info_tutorial_addon.html"