title: 'Series' objects are mutable, thus they cannot be hashed
body: <p>I have a groupedBy Series and am trying to perform a shift on each group. But the required shift per group is not always the same, hence I created a lookup dict from which I want to extract the shift of each respective item.</p>
  
  <p>My Code:</p>
  
  <pre><code>shifted = shifted.groupby(by=["itemID", "date"]).shift(lookUp[shifted["itemID"]][expectedLagName])
  </code></pre>
  
  <p>This does not work since shifted["itemID"] returns a dataframe this is mutable, but since its groupedBy there should be only a single value and I do not know how to get that. Any ideas?</p>
  
  <p>Reproducing Code:</p>
  
  <pre><code>data=range(1,101)
  df=pd.DataFrame(data=data)
  df.columns=["a"]
  df["b"]= round(df["a"]/5)
  lookUp={}
  for i in range(1,21):
      lookUp[i] = round(i/2)
  
  df = df.groupby(by=["b"]).shift(lookUp[df["b"]])
  print(df)
  </code></pre>