title: Convert pandas dataframe into a list of unique tuple
body: <p>What is the most efficient way to convert a pandas dataframe into a list of unique tuple?
  In the code below I am trying to extract a list of tuples containing all the unique <code>PostalCode</code> and <code>Age</code>.</p>
  
  <pre><code>from typing import NamedTuple, Sequence, Tuple
  
  import pandas as pd
  
  data = [["tom", 10, "ab 11"], ["nick", 14, "ab 22"], ["juli", 10, "ab 11"]]
  people = pd.DataFrame(data, columns=["Name", "Age", "PostalCode"])
  
  subset = pd.unique(people[["PostalCode", "Age"]].values.ravel())
  
  # This produce an error
  output = list(subset.itertuples(index=False))
  
  # Expected output
  # [('ab 11', 10), ('ab 22', 14)]
  </code></pre>