`astype(..., copy=False)` in `encode_values_into_bin_idx` emits Pandas4Warning on pandas ≥3.0 — drop the deprecated `copy` keyword

[xyf5432]

Summary

DataSynthesizer/datatypes/DateTimeAttribute.py calls Series.astype(..., copy=False),
which is deprecated in pandas 3.0:

File	Line
DataSynthesizer/datatypes/DateTimeAttribute.py	78 return encoded.astype(int, copy=False)

encoded is a pandas Series (self.data.map(...) / self.timestamps.map(...) +
concat(...)). Verified on pandas 3.0.5:

>>> s.astype(int, copy=False)
Pandas4Warning: The copy keyword is deprecated and will be removed in a
future version. Copy-on-Write is active in pandas since 3.0 which utilizes
a lazy copy mechanism that defers copies until necessary. Use .copy() to
make an eager copy if necessary.

Pandas4Warning is a DeprecationWarning subclass, so it is invisible
by default and does not fail CI — but it fires on every
encode_values_into_bin_idx() call under pandas ≥3.0, and the keyword
will be removed in a future version.

Suggested fix: version-guarded branch

Guard the call on the pandas version — keep copy=False on pandas <3.0
(where it is still meaningful: it avoids an extra copy when the dtype is
unchanged) and drop it on ≥3.0, following the pattern used in
NVIDIA/cuml#8142:

if PANDAS_VERSION < Version("3.0"):
    return encoded.astype(int, copy=False)
else:
    return encoded.astype(int)

with PANDAS_VERSION = Version(pd.__version__) at module level
(packaging is already a transitive dependency of pandas).

This is behaviour-preserving on every pandas version: the copy
keyword never affects the result of astype, only whether an extra
copy is made, and the branch keeps that behaviour exactly as it was on
each side of the boundary. Verified with runtime checks on pandas 2.3.3
and 3.0.5 (Series → fillna → branch):

• pandas 2.3.3 takes the copy=False branch, results identical.
• pandas 3.0.5 takes the plain branch: no Pandas4Warning is emitted,
  results identical (the copy keyword is a documented no-op under
  Copy-on-Write).

Installation does not bound pandas

setup.py declares pandas>=1.0.5 with no upper bound, so a fresh
pip install DataSynthesizer on current PyPI resolves pandas 3.x and the
warning fires whenever encode_values_into_bin_idx is used.

Specifications

• DataSynthesizer version: 0.1.13
• Python version: n/a (library code)
• Operating System: n/a

Description

See Summary and Suggested fix above.

What I Did

Install with a current pandas 3.x resolution and call encode_values_into_bin_idx on a datetime attribute:

Pandas4Warning: The copy keyword is deprecated and will be removed in a future version.