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 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# How to Build Transformer"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Generate Transformer from Method"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "from __future__ import annotations\n",
    "\n",
    "import numpy as np\n",
    "\n",
    "from dtoolkit.transformer.factory import methodtf_factory"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Generate a plus / minus constant transformer:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "def plus_constant(X: np.ndarray, constant: int | float) -> np.ndarray:\n",
    "    \"\"\"Plus constant to each element of ``X``\"\"\"\n",
    "\n",
    "    return X + constant\n",
    "\n",
    "\n",
    "def minus_constant(X: np.ndarray, constant: int | float) -> np.ndarray:\n",
    "    \"\"\"Minus constant to each element of ``X``\"\"\"\n",
    "\n",
    "    return X - constant\n",
    "\n",
    "\n",
    "PlusTF = methodtf_factory(plus_constant, minus_constant)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Use this transformer:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "a = np.array([1, 2, 3])\n",
    "tf = PlusTF(constant=1).update_invargs(constant=1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "tf.transform(a)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "tf.inverse_transform(a)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Build DataFrame Transformer"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Port `numpy`'s method to transformer."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "from dtoolkit.transformer import NumpyTF\n",
    "\n",
    "\n",
    "class MyTF(NumpyTF):\n",
    "    \"\"\"Doc here\"\"\"\n",
    "\n",
    "    transform_method = staticmethod(\"numpy's inner method\")"
   ]
  }
 ],
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