DOC : modified docs is HasTraits.traits and HasTraits.class_traits

 - change list -> dict to reflect what the code does
 - clarified how kwargs work (instead of just referencing enthought.traits).
 - fix classes -> class' spelling

IPython/utils/traitlets.py

@@ -530,27 +530,33 b' class HasTraits(py3compat.with_metaclass(MetaHasTraits, object)):'
 
     @classmethod
     def class_trait_names(cls, **metadata):
-        """Get a list of all the names of this classes traits.
+        """Get a list of all the names of this class' traits.
 
-        This method is just like the :meth:`trait_names` method, but is unbound.
+        This method is just like the :meth:`trait_names` method,
+        but is unbound.
         """
         return cls.class_traits(**metadata).keys()
 
     @classmethod
     def class_traits(cls, **metadata):
-        """Get a list of all the traits of this class.
+        """Get a `dict` of all the traits of this class.  The dictionary
+        is keyed on the name and the values are the TraitType objects.
 
         This method is just like the :meth:`traits` method, but is unbound.
 
         The TraitTypes returned don't know anything about the values
         that the various HasTrait's instances are holding.
 
-        This follows the same algorithm as traits does and does not allow
-        for any simple way of specifying merely that a metadata name
-        exists, but has any value.  This is because get_metadata returns
-        None if a metadata key doesn't exist.
+        The metadata kwargs allow functions to be passed in which
+        filter traits based on metadata values.  The functions should
+        take a single value as an argument and return a boolean.  If
+        any function returns False, then the trait is not included in
+        the output.  This does not allow for any simple way of
+        testing that a metadata name exists and has any
+        value because get_metadata returns None if a metadata key
+        doesn't exist.
         """
-        traits = dict([memb for memb in getmembers(cls) if \
+        traits = dict([memb for memb in getmembers(cls) if
                      isinstance(memb[1], TraitType)])
 
         if len(metadata) == 0:
@@ -571,21 +577,26 b' class HasTraits(py3compat.with_metaclass(MetaHasTraits, object)):'
         return result
 
     def trait_names(self, **metadata):
-        """Get a list of all the names of this classes traits."""
+        """Get a list of all the names of this class' traits."""
         return self.traits(**metadata).keys()
 
     def traits(self, **metadata):
-        """Get a list of all the traits of this class.
+        """Get a `dict` of all the traits of this class.  The dictionary
+        is keyed on the name and the values are the TraitType objects.
 
         The TraitTypes returned don't know anything about the values
         that the various HasTrait's instances are holding.
 
-        This follows the same algorithm as traits does and does not allow
-        for any simple way of specifying merely that a metadata name
-        exists, but has any value.  This is because get_metadata returns
-        None if a metadata key doesn't exist.
+        The metadata kwargs allow functions to be passed in which
+        filter traits based on metadata values.  The functions should
+        take a single value as an argument and return a boolean.  If
+        any function returns False, then the trait is not included in
+        the output.  This does not allow for any simple way of
+        testing that a metadata name exists and has any
+        value because get_metadata returns None if a metadata key
+        doesn't exist.
         """
-        traits = dict([memb for memb in getmembers(self.__class__) if \
+        traits = dict([memb for memb in getmembers(self.__class__) if
                      isinstance(memb[1], TraitType)])
 
         if len(metadata) == 0: