How to use the pytz.tzfile.build_tzinfo function in pytz

while start is not 0:
            tzpath = tzpath[start:]
            try:
                return pytz.timezone(tzpath)
            except pytz.UnknownTimeZoneError:
                pass
            start = tzpath.find("/")+1

    # No explicit setting existed. Use localtime
    for filename in ('etc/localtime', 'usr/local/etc/localtime'):
        tzpath = os.path.join(_root, filename)

        if not os.path.exists(tzpath):
            continue
        with open(tzpath, 'rb') as tzfile:
            return pytz.tzfile.build_tzinfo('local', tzfile)

    raise pytz.UnknownTimeZoneError('Can not find any timezone configuration')

def _tz_from_env(tzenv):
    if tzenv[0] == ':':
        tzenv = tzenv[1:]

    # TZ specifies a file
    if os.path.exists(tzenv):
        with open(tzenv, 'rb') as tzfile:
            return pytz.tzfile.build_tzinfo('local', tzfile)

    # TZ specifies a zoneinfo zone.
    try:
        tz = pytz.timezone(tzenv)
        # That worked, so we return this:
        return tz
    except pytz.UnknownTimeZoneError:
        raise pytz.UnknownTimeZoneError(
            "tzlocal() does not support non-zoneinfo timezones like %s. \n"
            "Please use a timezone in the form of Continent/City")

def _tz_from_env(tzenv):
    if tzenv[0] == ':':
        tzenv = tzenv[1:]

    # TZ specifies a file
    if os.path.exists(tzenv):
        with open(tzenv, 'rb') as tzfile:
            return pytz.tzfile.build_tzinfo('local', tzfile)

    # TZ specifies a zoneinfo zone.
    try:
        tz = pytz.timezone(tzenv)
        # That worked, so we return this:
        return tz
    except pytz.UnknownTimeZoneError:
        raise pytz.UnknownTimeZoneError(
            "tzlocal() does not support non-zoneinfo timezones like %s. \n"
            "Please use a timezone in the form of Continent/City")

if zone.upper() == 'UTC':
        return utc

    try:
        zone = ascii(zone)
    except UnicodeEncodeError:
        # All valid timezones are ASCII
        raise UnknownTimeZoneError(zone)

    zone = _case_insensitive_zone_lookup(_unmunge_zone(zone))
    if zone not in _tzinfo_cache:
        if zone in all_timezones_set:  # noqa
            fp = open_resource(zone)
            try:
                _tzinfo_cache[zone] = build_tzinfo(zone, fp)
            finally:
                fp.close()
        else:
            raise UnknownTimeZoneError(zone)

    return _tzinfo_cache[zone]

'''
    if zone.upper() == 'UTC':
        return utc

    try:
        zone = ascii(zone)
    except UnicodeEncodeError:
        # All valid timezones are ASCII
        raise UnknownTimeZoneError(zone)

    zone = _unmunge_zone(zone)
    if zone not in _tzinfo_cache:
        if zone in all_timezones_set:
            fp = open_resource(zone)
            try:
                _tzinfo_cache[zone] = build_tzinfo(zone, fp)
            finally:
                fp.close()
        else:
            raise UnknownTimeZoneError(zone)

    return _tzinfo_cache[zone]

'''
    if zone.upper() == 'UTC':
        return utc

    try:
        zone = ascii(zone)
    except UnicodeEncodeError:
        # All valid timezones are ASCII
        raise UnknownTimeZoneError(zone)

    zone = _unmunge_zone(zone)
    if zone not in _tzinfo_cache:
        if zone in all_timezones_set:
            fp = open_resource(zone)
            try:
                _tzinfo_cache[zone] = build_tzinfo(zone, fp)
            finally:
                fp.close()
        else:
            raise UnknownTimeZoneError(zone)

    return _tzinfo_cache[zone]

while start is not 0:
            tzpath = tzpath[start:]
            try:
                return pytz.timezone(tzpath)
            except pytz.UnknownTimeZoneError:
                pass
            start = tzpath.find("/")+1

    # No explicit setting existed. Use localtime
    for filename in ('etc/localtime', 'usr/local/etc/localtime'):
        tzpath = os.path.join(_root, filename)

        if not os.path.exists(tzpath):
            continue
        with open(tzpath, 'rb') as tzfile:
            return pytz.tzfile.build_tzinfo('local', tzfile)

    raise pytz.UnknownTimeZoneError('Can not find any timezone configuration')

'''
    if zone.upper() == 'UTC':
        return utc

    try:
        zone = ascii(zone)
    except UnicodeEncodeError:
        # All valid timezones are ASCII
        raise UnknownTimeZoneError(zone)

    zone = _unmunge_zone(zone)
    if zone not in _tzinfo_cache:
        if zone in all_timezones_set:
            fp = open_resource(zone)
            try:
                _tzinfo_cache[zone] = build_tzinfo(zone, fp)
            finally:
                fp.close()
        else:
            raise UnknownTimeZoneError(zone)

    return _tzinfo_cache[zone]

# This paragraph is auto-generated and may self-destruct at any time,
# courtesy of "make update". The original is in ‘utils/_boilerplate.py’.
# Thus, please do not remove the next line, or insert any blank lines.
#BP

# Utility code

from base64 import b64encode
from collections.abc import Mapping
from importlib import import_module
from datetime import datetime

import pytz
UTC = pytz.UTC
with open("/etc/localtime", 'rb') as tzfile:
    TZ = pytz.tzfile.build_tzinfo(str('local'), tzfile)


class _NOTGIVEN:
    pass


def uuidstr(u=None):
    if u is None:
        import uuid
        u = uuid.uuid1()
    return b64encode(u.bytes, altchars=b'-_').decode('ascii').rstrip('=')


def import_string(name):
    """Import a module, or resolve an attribute of a module."""
    name = str(name)