Add keys() method to Parameter class

This returns the names attribute, allowing **unpacking of Parameter subclasses.

pyqtgraph/parametertree/Parameter.py

@@ -677,6 +677,9 @@ class Parameter(QtCore.QObject):
             names = (names,)
         return self.param(*names).setValue(value)
 
+    def keys(self):
+        return self.names
+
     def child(self, *names):
         """Return a child parameter. 
         Accepts the name of the child or a tuple (path, to, child)

pyqtgraph/parametertree/tests/test_Parameter.py

@@ -34,3 +34,20 @@ def test_parameter_hasdefault_none(passdefault):
 
     p.setDefault(None)
     assert not p.hasDefault()
+
+def test_unpack_parameter():
+    # test that **unpacking correctly returns child name/value maps
+    params = [
+        dict(name='a', type='int', value=1),
+        dict(name='b', type='str', value='2'),
+        dict(name='c', type='float', value=3.0),
+    ]
+    p = Parameter.create(name='params', type='group', children=params)
+    result = dict(**p)
+
+    assert 'a' in result
+    assert result['a'] == 1
+    assert 'b' in result
+    assert result['b'] == '2'
+    assert 'c' in result
+    assert result['c'] == 3.0