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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 AddOperands(self, lhs, rhs):
 """Add an operand."""

    if isinstance(lhs, Expression) and isinstance(rhs, Expression):
      self.args = [lhs, rhs]
    else:
      raise errors.ParseError(
          'Expected expression, got {0:s} {1:s} {2:s}'.format(
              lhs, self.operator, rhs))