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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 _translate_src_register_oprnd(self, operand):
 """Translate source register operand to SMT expr. """

        reg_info = self._arch_alias_mapper.get(operand.name, None)

        if reg_info:
            var_base_name, offset = reg_info

            var_size = self._arch_regs_size[var_base_name]
        else:
            var_base_name = operand.name
            var_size = operand.size

        var_name = self._get_var_name(var_base_name)
        ret_val = self.make_bitvec(var_size, var_name)

        if reg_info:
            ret_val = smtfunction.extract(ret_val, offset, operand.size)

        return ret_val