added version property to VersionInfo & revised __str__

Author: JarryShaw

docs/source/pcapkit/corekit/version.rst

@@ -11,6 +11,8 @@ which is originally designed alike :class:`sys.version_info`.
    :no-members:
    :show-inheritance:
 
+   .. autoproperty:: version
+
    .. property:: major
       :type: int
 

pcapkit/corekit/version.py

@@ -13,5 +13,21 @@
 
 __all__ = ['VersionInfo']
 
-VersionInfo = collections.namedtuple('VersionInfo', ['major', 'minor'])
-VersionInfo.__doc__ = """VersionInfo is alike :class:`sys.version_info`."""
+
+class VersionInfo(collections.namedtuple('VersionInfo', ['major', 'minor'])):
+    """VersionInfo is alike :class:`sys.version_info`."""
+
+    __slots__ = ()
+
+    #: Major version.
+    major: int
+    #: Minor version.
+    minor: int
+
+    @property
+    def version(self) -> 'str':
+        """Return version string."""
+        return f'{self.major}.{self.minor}'
+
+    def __str__(self) -> 'str':
+        return f'{self.major}.{self.minor}'