Add type hints to seq()'s increment_by argument (#560)

* Add type hints for `increment_by` parameter in `seq` function

* Update CHANGELOG

* Fix mypy errors in `seq()` type hints

---------

Co-authored-by: Rust Saiargaliev <fly.amureki@gmail.com>

Author: Neutronlul

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Changed
 - docs: Update seq import in basic usage
+- Add type hints to `seq()`'s `increment_by` argument
 
 ### Removed
 - Drop mentions of model_mommy from the project. The old migration script is available in [the GitHub gist](https://gist.github.com/amureki/168b545105cb3e71f824351ffff507dc).

model_bakery/utils.py

@@ -1,4 +1,5 @@
 import datetime
+import decimal
 import importlib
 import inspect
 import itertools
@@ -50,7 +51,45 @@ def get_calling_module(levels_back: int) -> ModuleType | None:
     return inspect.getmodule(frame)
 
 
-def seq(value, increment_by=1, start=None, suffix=None):
+def _seq_datetime(
+    value: datetime.datetime | datetime.date | datetime.time,
+    increment_by: int | float | decimal.Decimal | datetime.timedelta,
+):
+    if not isinstance(increment_by, datetime.timedelta):
+        raise TypeError("datetime values require a timedelta increment_by")
+    if type(value) is datetime.date:
+        date: datetime.datetime = datetime.datetime.combine(
+            value, datetime.datetime.now().time()
+        )
+    elif type(value) is datetime.time:
+        date = datetime.datetime.combine(datetime.date.today(), value)
+    elif isinstance(value, datetime.datetime):
+        date = value
+    else:
+        raise TypeError("Unexpected value type")
+
+    epoch_datetime = datetime.datetime(1970, 1, 1, tzinfo=date.tzinfo)
+    start_seconds = (date - epoch_datetime).total_seconds()
+    increment_seconds = increment_by.total_seconds()
+    for n in itertools.count(increment_seconds, increment_seconds):
+        series_date = tz_aware(
+            datetime.datetime.fromtimestamp(start_seconds + n, tz=datetime.timezone.utc)
+        )
+
+        if type(value) is datetime.time:
+            yield series_date.time()
+        elif type(value) is datetime.date:
+            yield series_date.date()
+        else:
+            yield series_date
+
+
+def seq(
+    value,
+    increment_by: int | float | decimal.Decimal | datetime.timedelta = 1,
+    start: int | float | None = None,
+    suffix=None,
+):
     """Generate a sequence of values based on a running count.
 
     This function can be used to generate sequences of `int`, `float`,
@@ -60,8 +99,8 @@ def seq(value, increment_by=1, start=None, suffix=None):
     Args:
         value (object): the value at which to begin generation (this will
             be ignored for types `datetime`, `date`, and `time`)
-        increment_by (`int` or `float`, optional): the amount by which to
-            increment for each generated value (defaults to `1`)
+        increment_by (`int` or `float` or `decimal.Decimal` or `datetime.timedelta`, optional):
+            the amount by which to increment for each generated value (defaults to `1`)
         start (`int` or `float`, optional): the value at which the sequence
             will begin to add to `value` (if `value` is a `str`, `start` will
             be appended to it)
@@ -75,29 +114,10 @@ def seq(value, increment_by=1, start=None, suffix=None):
     _validate_sequence_parameters(value, increment_by, start, suffix)
 
     if isinstance(value, (datetime.datetime, datetime.date, datetime.time)):
-        if type(value) is datetime.date:
-            date = datetime.datetime.combine(value, datetime.datetime.now().time())
-        elif type(value) is datetime.time:
-            date = datetime.datetime.combine(datetime.date.today(), value)
-        else:
-            date = value
-
-        # convert to epoch time
-        epoch_datetime = datetime.datetime(1970, 1, 1, tzinfo=date.tzinfo)
-        start = (date - epoch_datetime).total_seconds()
-        increment_by = increment_by.total_seconds()
-        for n in itertools.count(increment_by, increment_by):
-            series_date = tz_aware(
-                datetime.datetime.fromtimestamp(start + n, tz=datetime.timezone.utc)
-            )
-
-            if type(value) is datetime.time:
-                yield series_date.time()
-            elif type(value) is datetime.date:
-                yield series_date.date()
-            else:
-                yield series_date
+        yield from _seq_datetime(value, increment_by)
     else:
+        if isinstance(increment_by, datetime.timedelta):
+            raise TypeError("non-datetime values do not support timedelta increment_by")
         for n in itertools.count(
             increment_by if start is None else start, increment_by
         ):