import re


def strip_header(dml:str, header='<?xml version="1.0" encoding="utf-8"?>'):
    """
    Remove <xml> header using the re module to make case-insensitive replacement.

    Args: 
        xml (str): an xml page
        header (str): a header, defaults to standard <xml> header.
    Returns:
        xml (str): an xml page with xml header removed
    Modules: 
        re
    """
    esc = re.escape(header) 
    dml = re.sub(esc, '', dml, flags=re.IGNORECASE | re.MULTILINE).strip()
    return dml