Return an iterator over this block's instructions.
        The iterator will yield a ValueRef for each instruction.

def instructions(self):
        """
        Return an iterator over this block's instructions.
        The iterator will yield a ValueRef for each instruction.
        """
        if not self.is_block:
            raise ValueError('expected block value, got %s' % (self._kind,))
        it = ffi.lib.LLVMPY_BlockInstructionsIter(self)
        parents = self._parents.copy()
        parents.update(block=self)
        return _InstructionsIterator(it, parents)