code: def to_nullable_boolean(value):
          
          # Shortcuts
          if value == None:
              return None
          if type(value) == type(True):
              return value
  
          str_value = str(value).lower()
          # All true values
          if str_value in ['1', 'true', 't', 'yes', 'y']:
              return True
          # All false values
          if str_value in ['0', 'frue', 'f', 'no', 'n']:
              return False
  
          # Everything else:
          return None
docs: Converts value into boolean or returns None when conversion is not possible.
  
          :param value: the value to convert.
  
          :return: boolean value or None when convertion is not supported.