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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 parse_vars_and_interpolations(self, string):
 """Parse a string for variables and interpolations, but don't treat anything else as Sass syntax. Returns an AST node. """

        # Shortcut: if there are no #s or $s in the string in the first place,
        # it must not have anything of interest.
        if '#' not in string and '$' not in string:
            return Literal(String.unquoted(string))
        return self.parse_expression(
            string, 'goal_interpolated_literal_with_vars')