from typing import Optional
from typing import Tuple
from typing import Any


def get_columns_from_str(columns: Optional[str],
                         separator: str = ',') -> Tuple[Any, ...]:
  """Converts columns input as separated string to tuples for further processing.

  A helper function to convert strings containing column names to tuples of
  column names.

  Args:
    columns: List of columns as a string with separators.
    separator: Character that separates the column names in the string.

  Returns:
    A tuple containing the columns names or empty if the column string doesn't
      exist or is empty.
  """
  if not columns:
    return ()
  return tuple(columns.split(separator))