nodes: 0, module; 1, function_definition; 2, function_name:_is_viable_phone_number; 3, parameters; 4, block; 5, identifier:number; 6, expression_statement; 7, if_statement; 8, expression_statement; 9, return_statement; 10, comment:"""Checks to see if a string could possibly be a phone number.
  
      At the moment, checks to see that the string begins with at least 2
      digits, ignoring any punctuation commonly found in phone numbers.  This
      method does not require the number to be normalized in advance - but does
      assume that leading non-number symbols have been removed, such as by the
      method _extract_possible_number.
  
      Arguments:
      number -- string to be checked for viability as a phone number
  
      Returns True if the number could be a phone number of some sort, otherwise
      False
      """; 11, comparison_operator:len(number) < _MIN_LENGTH_FOR_NSN; 12, block; 13, assignment; 14, call; 15, call; 16, identifier:_MIN_LENGTH_FOR_NSN; 17, return_statement; 18, identifier:match; 19, call; 20, identifier:bool; 21, argument_list; 22, identifier:len; 23, argument_list; 24, False; 25, identifier:fullmatch; 26, argument_list; 27, identifier:match; 28, identifier:number; 29, identifier:_VALID_PHONE_NUMBER_PATTERN; 30, identifier:number
code: def _is_viable_phone_number(number):
      """Checks to see if a string could possibly be a phone number.
  
      At the moment, checks to see that the string begins with at least 2
      digits, ignoring any punctuation commonly found in phone numbers.  This
      method does not require the number to be normalized in advance - but does
      assume that leading non-number symbols have been removed, such as by the
      method _extract_possible_number.
  
      Arguments:
      number -- string to be checked for viability as a phone number
  
      Returns True if the number could be a phone number of some sort, otherwise
      False
      """
      if len(number) < _MIN_LENGTH_FOR_NSN:
          return False
      match = fullmatch(_VALID_PHONE_NUMBER_PATTERN, number)
      return bool(match)