code: def yf(ticker, field, start=None, end=None, mrefresh=False):
      if field is None:
          field = "Adj Close"
  
      yfinance.pdr_override()
  
      tmp = pdata.get_data_yahoo(ticker, start=start, end=end)
  
      if tmp is None:
          raise ValueError(
              "failed to retrieve data for %s:%s" % (ticker, field)
          )
  
      if field:
          return tmp[field]
      else:
          return tmp
  
file_path: ffn/ffn/data.py
imports: import ffn
  import pandas
  import yfinance
  from packaging.version import Version
  from pandas_datareader import data
  from .None import utils
label_desc: Use image node_id 4 for calling a global function with example usage: yf(ticker, field, start, end, mrefresh) and returns: tmp, tmp