Repository: pandas-dev/pandas
File: pandas/core/indexes/base.py (Python)

Code before:
    # --------------------------------------------------------------------
    # Arithmetic & Logical Methods

    def __iadd__(self, other):
        # alias for __add__
        return self + other

    @final
    def __bool__(self) -> NoReturn:
        raise ValueError(
            f"The truth value of a {type(self).__name__} is ambiguous. "
            "Use a.empty, a.bool(), a.item(), a.any() or a.all()."
        )

    # --------------------------------------------------------------------
    # Set Operation Methods

    def _get_reconciled_name_object(self, other):
        """
        If the result of a set operation will be self,
        return a shallow copy of self.
        """
        name = get_op_result_name(self, other)
        if self.name is not name:
            return self.rename(name)
        return self.copy()

    @final
    def _validate_sort_keyword(self, sort) -> None:
        if sort not in [None, False, True]:
            raise ValueError(
                "The 'sort' keyword only takes the values of "
                f"None, True, or False; {sort} was passed."
            )

    @final
    def _dti_setop_align_tzs(self, other: Index, setop: str_t) -> tuple[Index, Index]:
        """
        With mismatched timezones, cast both to UTC.
        """
        # Caller is responsible for checking
        #  `self.dtype != other.dtype`
        if (
            isinstance(self, ABCDatetimeIndex)
            and isinstance(other, ABCDatetimeIndex)
            and self.tz is not None
            and other.tz is not None
        ):
            # GH#39328, GH#45357, GH#60080
            # If both timezones are the same, no need to convert to UTC
            if self.tz == other.tz:

Review comment (suggestion):
```suggestion
        return self.copy(deep=False)
```

I know that is the default, but for code readability I might add it explicitly (given the default for Series/DataFrame is True, one might expect that here as well; I was at least confused about when first looking at this)

Code after:
    # --------------------------------------------------------------------
    # Arithmetic & Logical Methods

    def __iadd__(self, other):
        # alias for __add__
        return self + other

    @final
    def __bool__(self) -> NoReturn:
        raise ValueError(
            f"The truth value of a {type(self).__name__} is ambiguous. "
            "Use a.empty, a.bool(), a.item(), a.any() or a.all()."
        )

    # --------------------------------------------------------------------
    # Set Operation Methods

    def _get_reconciled_name_object(self, other):
        """
        If the result of a set operation will be self,
        return a shallow copy of self.
        """
        name = get_op_result_name(self, other)
        if self.name is not name:
            return self.rename(name)
        return self.copy(deep=False)

    @final
    def _validate_sort_keyword(self, sort) -> None:
        if sort not in [None, False, True]:
            raise ValueError(
                "The 'sort' keyword only takes the values of "
                f"None, True, or False; {sort} was passed."
            )

    @final
    def _dti_setop_align_tzs(self, other: Index, setop: str_t) -> tuple[Index, Index]:
        """
        With mismatched timezones, cast both to UTC.
        """
        # Caller is responsible for checking
        #  `self.dtype != other.dtype`
        if (
            isinstance(self, ABCDatetimeIndex)
            and isinstance(other, ABCDatetimeIndex)
            and self.tz is not None
            and other.tz is not None
        ):
            # GH#39328, GH#45357, GH#60080
            # If both timezones are the same, no need to convert to UTC
            if self.tz == other.tz: