feat: add pandas decls

crates/erg_compiler/lib/external/pandas.d/__init__.d.er

@@ -0,0 +1,5 @@
+{
+    .DataFrame!;
+    .Series!;
+    .Index;
+} = pyimport "core/api"

crates/erg_compiler/lib/external/pandas.d/core.d/api.d.er

@@ -0,0 +1,3 @@
+{.DataFrame!;} = pyimport "./frame"
+{.Series!;} = pyimport "./series"
+{.Index;} = pyimport "./indexes/api"

crates/erg_compiler/lib/external/pandas.d/core.d/frame.d.er

@@ -0,0 +1,14 @@
+{.Index;} = pyimport "./indexes/api"
+
+# I := Nat, V := Obj
+.DataFrame!: (C: Type, I: Type, V: Type) -> ClassType
+.DataFrame!(C, I, V) <: Input(C)
+.DataFrame!(C, I, V) <: Input(I)
+.DataFrame!(C, I, V) <: Output(V)
+.DataFrame!.
+    __call__: |K, V, I|(dic: {K: [V; _]} or Iterable(Iterable(V)), index: [I; _] := [Nat; _]) -> .DataFrame!(K, I, V)
+    shape: (Nat, Nat)
+    index: .Index(_) # TODO
+    head: |C, I, V|(self: .DataFrame!(C, I, V), tail: Nat := {5}) -> .DataFrame!(C, I, V)
+    tail: |C, I, V|(self: .DataFrame!(C, I, V), tail: Nat := {5}) -> .DataFrame!(C, I, V)
+    info!: (self: .DataFrame!(_, _, _)) => NoneType

crates/erg_compiler/lib/external/pandas.d/core.d/indexes.d/api.d.er

@@ -0,0 +1 @@
+{.Index;} = pyimport "./base"

crates/erg_compiler/lib/external/pandas.d/core.d/indexes.d/base.d.er

@@ -0,0 +1,2 @@
+.Index: (T: Type) -> ClassType
+.Index(T) <: Output(T)

crates/erg_compiler/lib/external/pandas.d/core.d/series.d.er

@@ -0,0 +1,8 @@
+{.Index;} = pyimport "./indexes/api"
+
+# K := Nat, V := Obj
+.Series!: (K: Type, V: Type) -> ClassType
+.Series!(K, V) <: Input(K)
+.Series!(K, V) <: Output(V)
+.Series!.
+    __call__: |K, V|(iterable: Iterable(V), index: [K; _] or .Index(K) := [Nat; _]) -> .Series! K, V