该函数已在前一个单元格中定义，但错误提示未定义

Question

我正在使用 jupyter notebook。以下代码使用 metpy 包中定义的一些函数 (dewpoint_from_relative_humidity) 来定义一个新函数“calc”。

import numpy as np
import xarray as xr
from time import time
import matplotlib.pyplot as plt
from scipy.interpolate import interp1d
from metpy.units import units
from metpy.calc import cape_cin, dewpoint_from_relative_humidity, parcel_profile, most_unstable_cape_cin, mixed_layer_cape_cin
from metpy.calc import dewpoint_from_relative_humidity
from multiprocessing import Pool
from pytictoc import TicToc # conda install pytictoc -c ecf


data1  = xr.open_dataset(r'new.nc')
data = data1.sel(latitude = slice (50,45), longitude = slice(-110,-108))
data.r.values = data.r.values/100
data.t.values = data.t.values-273
data.t.attrs['units'] = 'degree_Celsius'
data.r.attrs['units'] = 'dimensionless'
data.level.attrs['units'] = 'hectopascal'

## reversing pressure levels descending
data = data.isel(level=slice(None, None, -1))
p = data.level

#Defining the calc function using the metpy functions: dewpointy_f_R_H and Most_unstabe_cape_cin
def calc(idata):
    p1 = idata[0] 
    t1 = idata[1]
    rh1 = idata[2]
    
    td1 = dewpoint_from_relative_humidity(t1,rh1)

    cape = most_unstable_cape_cin(p1, t1, td1)
    #print(cape)
    return cape

SP_emp = data.drop_vars(['t'])
SP_emp['cape'] = SP_emp['r']*0
SP_emp = SP_emp.drop_vars(['r'])

#Dropping 'level' dimension
SP_emp = SP_emp.mean(['level'])


from multiprocess import Pool
from pytictoc import TicToc

if __name__ ==  '__main__':
     pool = Pool(processes = 8)
    #num_processors = 4

mucape_res = np.zeros((data.t.time.size, data.t.latitude.size * data.t.longitude.size)) # time * lat * lon
print(mucape_res.shape)
    
for lat in data.latitude.values:
        for lon in data.longitude.values:
            for tim in data.time.values:
                t = TicToc()
                t.tic()
                Temp = data.t.sel(time =tim, latitude=lat, longitude = lon)
                #print(Temp)
                RH = data.r.sel(time =tim, latitude=lat, longitude = lon)
                #print(RH)
                #print(TD)
                sets = p,Temp,RH
                out = pool.map(calc,sets)
                #out = calc(set)
                cape_mag = out.magnitude
                SP_emp.cape.loc[dict(time = tim,longitude = lon, latitude = lat)] = cape_mag
                t.toc()
                #pool.close()

但是当在循环中进一步使用这个定义的函数时，会出现以下错误：

NameError: name 'dewpoint_from_relative_humidity' is not defined

如果之前已经在'calc'中定义了函数，为什么会出现错误，池或在新函数中定义本机函数的方式是否有问题？