numba-rvsdg/numba_rvsdg/core/datastructures/scfg.py:734: in restructure
    self.restructure_loop()
numba-rvsdg/numba_rvsdg/core/datastructures/scfg.py:712: in restructure_loop
    restructure_loop(self.region)
numba-rvsdg/numba_rvsdg/core/transformations.py:269: in restructure_loop
    loop_restructure_helper(scfg, loop)
numba-rvsdg/numba_rvsdg/core/transformations.py:34: in loop_restructure_helper
    headers, entries = scfg.find_headers_and_entries(loop)
numba-rvsdg/numba_rvsdg/core/datastructures/scfg.py:393: in find_headers_and_entries
    headers = {self.find_head()}
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = SCFG(graph={'1': PythonASTBlock(name='1', _jump_targets=('2', '3'), backedges=(), begin=-1, end=-1, tree=[<ast.Compare..._region_0', _jump_targets=(), backedges=(), kind='meta', parent_region=None, header=None, subregion=..., exiting=None))

    def find_head(self) -> str:
        """Finds the head block of the SCFG.

        Assuming the SCFG is closed, this will find the block
        that no other blocks are pointing to.

        Returns
        -------
        head: str
            Name of the head block of the graph.
        """
        heads = set(self.graph.keys())
        for name in self.graph.keys():
            block = self.graph[name]
            for jt in block.jump_targets:
                heads.discard(jt)
>       assert len(heads) == 1
E       AssertionError