collapse_child - Collapses a parent (which is the current node) and a given
  child node into the parent
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   collapse_child [-h] [-v] <child_instance_name>

   This command collapses the given child into the current node. After this
   command, the number of children of the current node will decrease by one.
   The variables in the child node will be renamed to reflect their original
   name.  For  example, if the current node is named "foo" and it has two
   children, "bar1" and "bar2", then after

   collapse_child bar1

   is executed, the name of any variable occuring in bar1, say "xvar" will be
   renamed "bar1$xvar". The new parent will have only the single child "bar2"
   (which can be seen by typing "ls").

   The user can use "cd" to traverse a hierarchy, go to a particular node. When
   the  user uses "write_blif" from a particular node, vis will write the
   circuit in this node out. However, the user might want to do synthesis on
   the entire circuit in the hierarchy. In that case, the hierarchy can be
   collapsed into a single node, by repeatedly using this command.

   Examples:

   collapse_child P1

   Collapse P1 into the current node.

   Command options:

   -h
          Print the command usage.

   -v
   Verbose mode.
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   Last updated on 20100410 00h02