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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def to_latlon(easting, northing, zone_number, zone_letter=None, northern=None, strict=True):
 """This function convert an UTM coordinate into Latitude and Longitude Parameters easting: int Easting value of UTM coordinate northing: int Northing value of UTM coordinate zone number: int Zone Number is represented with global map numbers of an UTM Zone Numbers Map. More information see utmzones [1]_ zone_letter: str Zone Letter can be represented as string values. Where UTM Zone Designators can be accessed in [1]_ northern: bool You can set True or False to set this parameter. Default is None .. _[1]: http://www.jaworski.ca/utmzones.htm """

    if not zone_letter and northern is None:
        raise ValueError('either zone_letter or northern needs to be set')

    elif zone_letter and northern is not None:
        raise ValueError('set either zone_letter or northern, but not both')

    if strict:
        if not in_bounds(easting, 100000, 1000000, upper_strict=True):
            raise OutOfRangeError('easting out of range (must be between 100.000 m and 999.999 m)')
        if not in_bounds(northing, 0, 10000000):
            raise OutOfRangeError('northing out of range (must be between 0 m and 10.000.000 m)')
    
    check_valid_zone(zone_number, zone_letter)
    
    if zone_letter:
        zone_letter = zone_letter.upper()
        northern = (zone_letter >= 'N')

    x = easting - 500000
    y = northing

    if not northern:
        y -= 10000000

    m = y / K0
    mu = m / (R * M1)

    p_rad = (mu +
             P2 * mathlib.sin(2 * mu) +
             P3 * mathlib.sin(4 * mu) +
             P4 * mathlib.sin(6 * mu) +
             P5 * mathlib.sin(8 * mu))

    p_sin = mathlib.sin(p_rad)
    p_sin2 = p_sin * p_sin

    p_cos = mathlib.cos(p_rad)

    p_tan = p_sin / p_cos
    p_tan2 = p_tan * p_tan
    p_tan4 = p_tan2 * p_tan2

    ep_sin = 1 - E * p_sin2
    ep_sin_sqrt = mathlib.sqrt(1 - E * p_sin2)

    n = R / ep_sin_sqrt
    r = (1 - E) / ep_sin

    c = _E * p_cos**2
    c2 = c * c

    d = x / (n * K0)
    d2 = d * d
    d3 = d2 * d
    d4 = d3 * d
    d5 = d4 * d
    d6 = d5 * d

    latitude = (p_rad - (p_tan / r) *
                (d2 / 2 -
                 d4 / 24 * (5 + 3 * p_tan2 + 10 * c - 4 * c2 - 9 * E_P2)) +
                 d6 / 720 * (61 + 90 * p_tan2 + 298 * c + 45 * p_tan4 - 252 * E_P2 - 3 * c2))

    longitude = (d -
                 d3 / 6 * (1 + 2 * p_tan2 + c) +
                 d5 / 120 * (5 - 2 * c + 28 * p_tan2 - 3 * c2 + 8 * E_P2 + 24 * p_tan4)) / p_cos

    return (mathlib.degrees(latitude),
            mathlib.degrees(longitude) + zone_number_to_central_longitude(zone_number))