from typing import Tuple


def _lex_quoted(header: str) -> Tuple[str, str]:
    """
    >>> _lex_quoted('"abc";a=10')
    ('"abc"', ';a=10')
    >>> _lex_quoted('a=10')
    ('', 'a=10')
    """
    if header[0] != '"':
        return "", header
    end_quote_pos = header.find('"', 1)
    return header[: end_quote_pos + 1], header[end_quote_pos + 1 :]