This library provides the common functionality for searching and
 managing packages as well as information about packages.
 Higher-level package managers can depend upon this library.
 .
 This includes:
  * retrieval of information about packages from multiple sources
  * retrieval of packages and all dependent packages
    needed to satisfy a request either through an internal
    solver or by interfacing with an external one
  * authenticating the sources and validating the retrieved data
  * installation and removal of packages in the system
  * providing different transports to retrieve data over cdrom, ftp,
    http(s), rsh as well as an interface to add more transports like
    tor+http(s) (apt-transport-tor).