title: i have this error can anyone tell me the solution
body: <p>This is my code:</p>
  
  <pre><code>import pandas as pd
  import numpy as np
  
  # read dataframe
  df = pd.read_csv("loc-brightkite_totalCheckins.txt", usecols=["location_id", "user"], delim_whitespace=True, names=["user", "check_in_time", "latitude", "longitude", "location_id"])
  
  # remove duplicates (regarding location and user)
  df = df.drop_duplicates(subset=["user", "location_id"])
  
  #group by the locations, make each a series of users, count users
  distinct_location_users = df.groupby('location_id')['user'].agg(lambda user_series: len(user_series))
  
  # print top 10 locations
  top_10 = distinct_location_users.order().tail(11)
  
  print top_10
  
  top_10.plot(kind="bar")
  </code></pre>
  
  <p>I'm getting this error:</p>
  
  <pre><code>TypeError                                 Traceback (most recent call last)
  &lt;ipython-input-7-5c9c8115e794&gt; in &lt;module&gt;()
        6 
        7 # remove duplicates (regarding location and user)
  ----&gt; 8 df = df.drop_duplicates(subset=["user", "location_id"])
        9 
       10 #group by the locations, make each a series of users, count users
  
  TypeError: drop_duplicates() got an unexpected keyword argument 'subset'
  </code></pre>