code: def is_valid_identifier(identifier):
      
      if not isinstance(identifier, basestring):
          return False
  
      if len(identifier) > 100 or len(identifier) < 1:
          return False
  
      condensed_form = set(list(identifier.lower()))
      return condensed_form.issubset(VALID_IDENTIFIER_SET)
docs: Checks if the given identifier is valid or not. A valid
      identifier may consists of the following characters with a
      maximum length of 100 characters, minimum of 1 character.
  
      Valid characters for an identifier,
          - A to Z
          - a to z
          - 0 to 9
          - _ (underscore)
          - - (hypen)