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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_cachedir_bsig(self):
 """ Return the signature for a cached file, including its children. It adds the path of the cached file to the cache signature, because multiple targets built by the same action will all have the same build signature, and we have to differentiate them somehow. """

        try:
            return self.cachesig
        except AttributeError:
            pass

        # Collect signatures for all children
        children = self.children()
        sigs = [n.get_cachedir_csig() for n in children]
        # Append this node's signature...
        sigs.append(self.get_contents_sig())
        # ...and it's path
        sigs.append(self.get_internal_path())
        # Merge this all into a single signature
        result = self.cachesig = SCons.Util.MD5collect(sigs)
        return result