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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 psychrometric_vapor_pressure_wet(dry_bulb_temperature, wet_bulb_temperature, pressure, psychrometer_coefficient=6.21e-4 / units.kelvin):
 r"""Calculate the vapor pressure with wet bulb and dry bulb temperatures. This uses a psychrometric relationship as outlined in [WMO8-2014]_, with coefficients from [Fan1987]_. Parameters dry_bulb_temperature: `pint.Quantity` Dry bulb temperature wet_bulb_temperature: `pint.Quantity` Wet bulb temperature pressure: `pint.Quantity` Total atmospheric pressure psychrometer_coefficient: `pint.Quantity`, optional Psychrometer coefficient. Defaults to 6.21e-4 K^-1. Returns ------- `pint.Quantity` Vapor pressure Notes ----- .. math:: e' = e'_w(T_w) - A p (T - T_w) * :math:`e'` is vapor pressure * :math:`e'_w(T_w)` is the saturation vapor pressure with respect to water at temperature :math:`T_w` * :math:`p` is the pressure of the wet bulb * :math:`T` is the temperature of the dry bulb * :math:`T_w` is the temperature of the wet bulb * :math:`A` is the psychrometer coefficient Psychrometer coefficient depends on the specific instrument being used and the ventilation of the instrument. See Also -------- saturation_vapor_pressure """

    return (saturation_vapor_pressure(wet_bulb_temperature) - psychrometer_coefficient
            * pressure * (dry_bulb_temperature - wet_bulb_temperature).to('kelvin'))