try

solenoids/__init__.py

@@ -0,0 +1,17 @@
+__all__ = []
+
+import pkgutil
+import inspect
+
+__path__ = pkgutil.extend_path(__path__, __name__)
+
+for loader, name, is_pkg in pkgutil.walk_packages(__path__):
+    module = loader.find_module(name).load_module(name)
+
+    for name, value in inspect.getmembers(module):
+        if name.startswith('__'):
+            continue
+
+        globals()[name] = value
+        __all__.append(name)
+