diff --git a/compiler/erg_compiler/lib/pystd/heapq.d.er b/compiler/erg_compiler/lib/pystd/heapq.d.er
new file mode 100644
index 00000000..99aa0197
--- /dev/null
+++ b/compiler/erg_compiler/lib/pystd/heapq.d.er
@@ -0,0 +1,4 @@
+.heappush!: |T: Type|(heap: Iterable(T), item: T) => NoneType # TODO: Push!
+.heappop!: |T: Type|(heap: Iterable(T)) => T # TODO: Pop!
+.heappushpop!: |T: Type|(heap: Iterable(T), item: T) => T # TODO: Push! and Pop!
+.heapify!: (heap: Array(Obj, _)) => NoneType
diff --git a/compiler/erg_compiler/lib/pystd/http.d/server.d.er b/compiler/erg_compiler/lib/pystd/http.d/server.d.er
new file mode 100644
index 00000000..84da10e2
--- /dev/null
+++ b/compiler/erg_compiler/lib/pystd/http.d/server.d.er
@@ -0,0 +1,5 @@
+.HTTPServer: ClassType
+.ThreadingServer: ClassType
+.BaseHTTPReqeustHandler: ClassType
+.SimpleHTTPRequestHandler: ClassType
+.CGIHTTPRequestHandler: ClassType
diff --git a/compiler/erg_compiler/lib/pystd/inspect.d.er b/compiler/erg_compiler/lib/pystd/inspect.d.er
new file mode 100644
index 00000000..00ea9ed7
--- /dev/null
+++ b/compiler/erg_compiler/lib/pystd/inspect.d.er
@@ -0,0 +1,2 @@
+.FrameInfo: ClassType
+.Traceback: ClassType
diff --git a/compiler/erg_compiler/lib/pystd/pydoc.d.er b/compiler/erg_compiler/lib/pystd/pydoc.d.er
new file mode 100644
index 00000000..e69de29b
diff --git a/compiler/erg_compiler/lib/pystd/socketserver.d.er b/compiler/erg_compiler/lib/pystd/socketserver.d.er
new file mode 100644
index 00000000..505f9902
--- /dev/null
+++ b/compiler/erg_compiler/lib/pystd/socketserver.d.er
@@ -0,0 +1,17 @@
+.TCPServer: ClassType
+.UDPServer: ClassType
+.UnixStreamServer: ClassType
+.UnixDatagramServer: ClassType
+
+.ForkingMixIn: ClassType
+.ThreadingMixIn: ClassType
+
+.ForkingTCPServer: ClassType
+.ForkingUDPServer: ClassType
+.ThreadingTCPServer: ClassType
+.ThreadingUDPServer: ClassType
+
+.BaseServer: ClassType
+.BaseRequestHandler: ClassType
+.StreamRequestHandler: ClassType
+.DatagramRequestHandler: ClassType
diff --git a/compiler/erg_compiler/lib/pystd/threading.d.er b/compiler/erg_compiler/lib/pystd/threading.d.er
new file mode 100644
index 00000000..cab7122a
--- /dev/null
+++ b/compiler/erg_compiler/lib/pystd/threading.d.er
@@ -0,0 +1,23 @@
+.Thread!: ClassType
+.Thread!.name: Str
+.Thread!.daemon: Bool
+.Thread!.ident: Nat or NoneType # TODO: Pos or NoneType
+.Thread!.native_id: Nat or NoneType
+.Thread!.start!: (self: .Thread!) => NoneType
+.Thread!.run!: (self: .Thread!) => NoneType
+.Thread!.join!: (self: .Thread!, timeout := Nat or NoneType) => NoneType
+.Thread!.is_alive: (self: .Thread!) -> Bool
+
+.Local! = 'local': ClassType
+
+.Lock!: ClassType
+.RLock!: ClassType
+.Condition!: ClassType
+.Semaphore!: ClassType
+.BoundedSemaphore!: ClassType
+.Event!: ClassType
+.Timer!: ClassType
+.Barrier!: ClassType
+.BrokenBarrierError: ClassType
+
+.active_count!: () => Nat
diff --git a/compiler/erg_compiler/lib/pystd/traceback.d.er b/compiler/erg_compiler/lib/pystd/traceback.d.er
new file mode 100644
index 00000000..3af40667
--- /dev/null
+++ b/compiler/erg_compiler/lib/pystd/traceback.d.er
@@ -0,0 +1,5 @@
+inspect = pyimport "inspect"
+
+.print_tb!: (tb: inspect.Traceback, limit := Nat or NoneType, file := File! or NoneType) => NoneType
+
+.TracebackExeption: ClassType
diff --git a/compiler/erg_compiler/lib/pystd/types.d.er b/compiler/erg_compiler/lib/pystd/types.d.er
new file mode 100644
index 00000000..57330b3b
--- /dev/null
+++ b/compiler/erg_compiler/lib/pystd/types.d.er
@@ -0,0 +1,24 @@
+.NoneType: ClassType
+.FunctionType: ClassType
+.LambdaType: ClassType
+.GeneratorType: ClassType
+.CoroutineType: ClassType
+.AsyncGeneratorType: ClassType
+.CodeType: ClassType
+.CellType: ClassType
+.MethodType: ClassType
+.BuiltinFunctionType: ClassType
+.BuiltinMethodType: ClassType
+.WrapperDescriptorType: ClassType
+.MethodWrapperType: ClassType
+.NotImplementedType: ClassType
+.MethodDescriptorType: ClassType
+.ClassMethodDescriptorType: ClassType
+.ModuleType: ClassType
+.EllipsisType: ClassType
+.GenericAlias: (Type, GenericTuple) -> ClassType # TODO: Tuple Type
+.UnionType: (Type, Type) -> Type
+
+.TracebackType: ClassType
+.FrameType: ClassType
+.MappingProxyType: ClassType