<?xml version="1.0" encoding="UTF-8"?>
<library>
  <book id="1">
    <title>The Python Guide</title>
    <author>Elena Rodriguez</author>
    <year>2023</year>
    <price currency="USD">29.99</price>
    <available>true</available>
    <tags>
      <tag>programming</tag>
      <tag>python</tag>
    </tags>
  </book>
</library>

from dataclasses import dataclass
from typing import List, Optional
import xml.etree.ElementTree as ET

@dataclass
class Price:
    currency: str
    value: float

@dataclass
class Book:
    id: int
    title: str
    author: str
    year: int
    price: Price
    available: bool
    tags: List[str]

@dataclass
class Library:
    books: List[Book]

    @classmethod
    def from_xml(cls, xml_string: str) -> 'Library':
        root = ET.fromstring(xml_string)
        # XML parsing implementation...