feature: Convert tests to doctests and add example

Signed-off-by: John Andersen <[email protected]>

Author: Byambaa0325

CHANGELOG.md

@@ -18,6 +18,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Ability to run a subflow as if it were an operation using the
   `dffml.dataflow.run` operation.
 - Support for operations without inputs.
+- Partial doctestable examples to `features.py`
 ### Fixed
 - New model tutorial mentions file paths that should be edited.
 - DataFlow is no longer a dataclass to prevent it from being exported

dffml/feature/feature.py

@@ -113,6 +113,27 @@ class and implement the fetch, parse, and calc methods. These methods are
     Once the appropriate data is fetched the parse method is responsible for
     storing the parts of that data which will be used to calculate in the
     subclass
+
+    Examples
+    --------
+
+    Define a feature using load_def:
+    >>> feature = Feature.load_def("example", "float", 10)
+    >>> feature.dtype()
+    float
+    >>> feature.NAME
+    "example"
+    >>> feature.length()
+    10
+
+    Defining a feature directly using DefFeature:
+    >>> feature = DefFeature("example2", "int", 20)
+    >>> feature.dtype()
+    int
+    >>> feature.NAME
+    "example2"
+    >>> feature.length()
+    20
     """
 
     LOGGER = LOGGER.getChild("Feature")
@@ -147,6 +168,13 @@ def _fromdict(cls, **kwargs):
     def dtype(self) -> Type:
         """
         Models need to know a Feature's datatype.
+
+        Examples
+        --------
+
+        >>> feature = Feature()
+        >>> feature.dtype()
+        int
         """
         self.LOGGER.warning("%s dtype unimplemented", self)
         return int
@@ -155,6 +183,13 @@ def length(self) -> int:
         """
         Models need to know a Feature's length, 1 means single value, more than
         that is the length of the array calc returns.
+
+        Examples
+        --------
+
+        >>> feature = Feature()
+        >>> feature.length()
+        1
         """
         self.LOGGER.warning("%s length unimplemented", self)
         return 1