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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_join_cols(by_entry):
 """ helper function used for joins builds left and right join list for join function """

  left_cols = []
  right_cols = []
  for col in by_entry:
    if isinstance(col, str):
      left_cols.append(col)
      right_cols.append(col)
    else:
      left_cols.append(col[0])
      right_cols.append(col[1])
  return left_cols, right_cols