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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_reaction_equation_string(equation, default_compartment):
 """Parse a string representation of a reaction equation. Converts undefined compartments to the default compartment. """

    def _translate_compartments(reaction, compartment):
        """Translate compound with missing compartments.

        These compounds will have the specified compartment in the output.
        """
        left = (((c.in_compartment(compartment), v)
                 if c.compartment is None else (c, v))
                for c, v in reaction.left)
        right = (((c.in_compartment(compartment), v)
                  if c.compartment is None else (c, v))
                 for c, v in reaction.right)
        return Reaction(reaction.direction, left, right)

    eq = _REACTION_PARSER.parse(equation).normalized()
    return _translate_compartments(eq, default_compartment)