def __init__(self, install=False, passthru=None):
self.entries    = {}<EOL>self._installed = False<EOL>self.impostors  = dict()<EOL>self.originals  = dict()<EOL>self.vaporized  = None<EOL>self.fds        = dict()<EOL>self.passthru   = passthru or []<EOL>if self.passthru:<EOL><INDENT>if not morph.isseq(self.passthru):<EOL><INDENT>self.passthru = [self.passthru]<EOL><DEDENT>self.passthru = [re.compile(expr) if morph.isstr(expr) else expr<EOL>for expr in self.passthru]<EOL><DEDENT>self._makeImpostors()<EOL>if install:<EOL><INDENT>self.install()<EOL><DEDENT>
:Parameters:

install : bool, optional, default: false

  Flag indicating whether or not this overlay should be
  installed upon instantiation.

passthru : list({str, regex}), optional, default: none

  A regular expression (or list thereof) that will be matched
  against any file that is operated on; if it matches, no overlay
  will be applied, i.e. this list excludes a set of files. The
  specified regexes can be either strings or re.RegexObject
  instances. Note that these regexes will be given only the
  fully-dereferenced paths to be tested.