
  -spec processes() -> [pid()].

  Returns a list of process identifiers corresponding to all the
  processes currently existing on the local node.

  Notice that an exiting process exists, but is not alive. That is, 
  is_process_alive/1 returns false for an exiting process, but
  its process identifier is part of the result returned from 
  processes/0.

  Example:

    > processes().
    [<0.0.0>,<0.2.0>,<0.4.0>,<0.5.0>,<0.7.0>,<0.8.0>]
