Revert "Revert "Parameter: make port a weakref""

This reverts commit cf2fb8e.

psyneulink/core/globals/parameters.py

@@ -1057,7 +1057,6 @@ def __init__(
             reference=reference,
             dependencies=dependencies,
             initializer=initializer,
-            port=port,
             mdf_name=mdf_name,
             specify_none=specify_none,
             _inherited=_inherited,
@@ -1077,6 +1076,8 @@ def __init__(
         self.__inherited = False
         self._inherited = _inherited
 
+        self.port = port
+
     def __repr__(self):
         return '{0} :\n{1}'.format(super(types.SimpleNamespace, self).__repr__(), str(self))
 
@@ -1814,6 +1815,20 @@ def _set_spec(self, value):
             value = self._parse(value)
         super().__setattr__('spec', value)
 
+    @property
+    def port(self):
+        try:
+            return self._port()
+        except TypeError:
+            return self._port
+
+    @port.setter
+    def port(self, p):
+        if p is None:
+            self._port = None
+        else:
+            self._port = weakref.ref(p)
+
 
 class _ParameterAliasMeta(type):
     # these will not be taken from the source