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Given the following text description, write Python code to implement the functionality described below step by step
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Description:
 The $\alpha_s$ method
Very similar to the t-plot method, the $\alpha_s$ method compares an isotherm on
a porous material with one that was taken on a reference non-porous surface. The
reference isotherm should be measured over a wide pressure range, to be able to
compare loading values. First, make sure the data is imported notebook.
Step1:  Unfortunately, we don't have a reference isotherm in our data. We are instead
going to be creative and assume that the adsorption on the silica ($SiO_2$
sample) is a good representation of an adsorption on a non-porous version of the
MCM-41 sample. Let's try
Step2:  The data in our reference isotherm is on a smaller range than that in the
isotherm that we want to calculate! We are going to be creative again and first
model the adsorption behaviour using a ModelIsotherm.
Step3:  With our model fitting the data pretty well, we can now try the $\alpha_s$ method again.
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Python Code:
# import isotherms
%run import.ipynb
# import the characterisation module
import pygaps.characterisation as pgc
Explanation: The $\alpha_s$ method
Very similar to the t-plot method, the $\alpha_s$ method compares an isotherm on
a porous material with one that was taken on a reference non-porous surface. The
reference isotherm should be measured over a wide pressure range, to be able to
compare loading values. First, make sure the data is imported notebook.
End of explanation
iso_1 = next(i for i in isotherms_n2_77k if i.material == 'MCM-41')
iso_2 = next(i for i in isotherms_n2_77k if i.material == 'SiO2')
print(iso_1.material)
print(iso_2.material)
try:
    results = pgc.alpha_s(iso_1, reference_isotherm=iso_2, verbose=True)
except Exception as e:
    print('ERROR!:', e)
Explanation: Unfortunately, we don't have a reference isotherm in our data. We are instead
going to be creative and assume that the adsorption on the silica ($SiO_2$
sample) is a good representation of an adsorption on a non-porous version of the
MCM-41 sample. Let's try:
End of explanation
import pygaps
model = pygaps.ModelIsotherm.from_pointisotherm(iso_2, model='BET', verbose=True)
Explanation: The data in our reference isotherm is on a smaller range than that in the
isotherm that we want to calculate! We are going to be creative again and first
model the adsorption behaviour using a ModelIsotherm.
End of explanation
results = pgc.alpha_s(iso_1, model, verbose=True)
Explanation: With our model fitting the data pretty well, we can now try the $\alpha_s$ method again.
End of explanation
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