'Series' object is not callable - linspace function

import numpy as np
import matplotlib.pyplot as plt
import pandas as pd
import statsmodels.api as sm

twitter_data = pd.read_csv('result.csv')

#histogram of x axis followers and y axis retweets
hist1,edges1 = np.histogram(twitter_data.friends)


#results of x axis retwx and y axis followers 
y = twitter_data.retwc
X = twitter_data.followers
X = sm.add_constant(X)

lr_model = sm.OLS(y,X).fit()


#scatter plot full for retc and followers

X_prime = np.linspace(X.followers.min(), X.followers().max(),100)
X_prime = sm.add_constant(X_prime)

I am getting error

series object not callable

and it is pointing to the X_prime = np.linspace(X.followers.min(), X.followers().max(),100) line

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