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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 _iter_symbols(code):
 """ Iterate all the variable names in the given expression. Example: * ``self.foobar`` yields ``self`` * ``self[foobar]`` yields `self`` and ``foobar`` """

        for node in ast.walk(ast.parse(code)):
            if isinstance(node, ast.Name):
                yield node.id