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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 has_pkgconfig(self):
 """Returns whether ``pkg-config`` is available on the current system and it knows about igraph or not."""

        if self._has_pkgconfig is None:
            if self.use_pkgconfig:
                line, exit_code = get_output("pkg-config igraph")
                self._has_pkgconfig = (exit_code == 0)
            else:
                self._has_pkgconfig = False
        return self._has_pkgconfig