The launchpad web service's top-level collections provide access to
Launchpad-wide objects like projects and people.

    >>> from launchpadlib.testing.helpers import salgado_with_full_permissions
    >>> launchpad = salgado_with_full_permissions.login()

It's possible to do key-based lookups on the top-level
collections. The bug collection does lookups by bug ID.

    >>> launchpad.bugs[1].id
    1

The person collection does lookups by a person's Launchpad name.

    >>> launchpad.people['salgado'].name
    u'salgado'

The project collection does lookups by project name.

    >>> launchpad.projects['firefox'].name
    u'firefox'

The project group collection does lookups by project group name.

    >>> launchpad.project_groups['firefox'].name
    u'firefox'

The distribution collection does lookups by distribution name.

    >>> launchpad.distributions['ubuntu'].name
    u'ubuntu'

You can iterate over the top-level collections.

    >>> sorted([project.name for project in launchpad.projects])
    [u'a52dec', ... u'upstart']

But it's almost always better to slice them.

    >>> sorted([project.name for project in launchpad.projects[:2]])
    [u'landscape', u'redfish']
