title: Pandas can't find columns, ValueError
body: <pre><code>import numpy as np
  import matplotlib.pyplot as plt
  import pandas as pd
  
  symbols = ["AAPL", "GLD", "TSLA", "GBL", "GOOGL"]
  
  def compare_security(symbols):
      start_date = "01-01-2019"
      end_date = "01-12-2020"
      dates = pd.date_range(start_date, end_date)
  
      df1 = pd.DataFrame(index=dates)
      df_SPY = pd.read_csv(
          "https://www.alphavantage.co/query?function=TIME_SERIES_DAILY_ADJUSTED&amp;symbol=SPY&amp;apikey=XXXX&amp;datatype=csv",
          index_col="timestamp", usecols=["timestamp", "adjusted_close"], parse_dates=True, na_values=['nan'])
      df_SPY = df_SPY.rename(columns={"adjusted_close": "SPY"})
      df1 = df1.join(df_SPY, how="inner")
  
      for symbol in symbols:
          df_temp= pd.read_csv("https://www.alphavantage.co/query?function=TIME_SERIES_DAILY_ADJUSTED&amp;symbol={}&amp;apikey=XXXX&amp;datatype=csv".format(symbol),
              index_col = "timestamp", usecols = ["timestamp", "adjusted_close"], parse_dates=True, na_values=['nan'])
          df_temp = df_temp.rename(columns={"adjusted_close":symbol})
          df1 = df1.join(df_temp)
      return df1
  
  def test_run():
      df = compare_security(symbols)
      print(df)
      df.plot()
      plt.title(symbols)
      plt.show()
  
  if __name__ == "__main__":
      test_run()
  </code></pre>
  
  <p>It reads the error "ValueError: Usecols do not match columns, columns expected but not found: ['timestamp', 'adjusted_close']"</p>
  
  <p>However, I checked all the files the code would retrieve and all of them have the respective columns. Any clarification as to where I went wrong would be greatly appreciated.</p>