code: def test_inflate_existing_currency_col(dataframe):
      """Test currency inflation updates existing column."""
      initialval = dataframe["a"].sum()
      # Pulled raw values from API website for USA 2018 and 2015
      inflator = _inflate_currency(
          "USA", currency_year=2018, to_year=2015
      )
      df = dataframe.inflate_currency(
          "a",
          country="USA",
          currency_year=2018,
          to_year=2015,
          make_new_column=False,
      )
      updatedval = df["a"].sum()
      assert (initialval * inflator) == pytest.approx(updatedval)
  
file_path: pyjanitor/tests/finance/test_inflate_currency.py
imports: import pytest
  import requests
  from janitor.finance import _inflate_currency, inflate_currency
label_desc: Use image node_id 3 for calling a global function with example usage: test_inflate_existing_currency_col(dataframe) without return types