code: def filter_non_greek(input_str: str) -> str:
      """Takes string with mixed Greek and non-Greek characters,
      and returns string with non-Greek characters removed.
  
      >>> from cltk.alphabet import grc
      >>> str_mixed_greek = "παρακλίνασ᾽ ἐπέκρανεν [744] δὲ γάμου πικρὰς τελευτάς, [745] δύσεδρος καὶ δυσόμιλος [746]"
      >>> grc.filter_non_greek(str_mixed_greek)
      'παρακλίνασ᾽ ἐπέκρανεν  δὲ γάμου πικρὰς τελευτάς  δύσεδρος καὶ δυσόμιλος'
      """
      greek_alphabet = (
          LOWER
          + LOWER_ACUTE
          + LOWER_BREVE
          + LOWER_CIRCUMFLEX
          + LOWER_CONSONANTS
          + LOWER_DIAERESIS
          + LOWER_DIAERESIS_ACUTE
          + LOWER_DIAERESIS_CIRCUMFLEX
          + LOWER_DIAERESIS_GRAVE
          + LOWER_GRAVE
          + LOWER_MACRON
          + [LOWER_RHO]
          + LOWER_ROUGH
          + [LOWER_RHO_ROUGH]
          + [LOWER_RHO_SMOOTH]
          + LOWER_ROUGH_ACUTE
          + LOWER_ROUGH_CIRCUMFLEX
          + LOWER_ROUGH_GRAVE
          + LOWER_SMOOTH
          + LOWER_SMOOTH_ACUTE
          + LOWER_SMOOTH_CIRCUMFLEX
          + LOWER_SMOOTH_GRAVE
          + UPPER
          + UPPER_ACUTE
          + UPPER_BREVE
          + UPPER_CONSONANTS
          + UPPER_DIAERESIS
          + UPPER_GRAVE
          + UPPER_MACRON
          + [UPPER_RHO]
          + UPPER_ROUGH
          + [UPPER_RHO_ROUGH]
          + UPPER_ROUGH_ACUTE
          + UPPER_ROUGH_CIRCUMFLEX
          + UPPER_ROUGH_GRAVE
          + UPPER_SMOOTH
          + UPPER_SMOOTH_ACUTE
          + UPPER_SMOOTH_CIRCUMFLEX
          + UPPER_SMOOTH_GRAVE
          + NUMERAL_SIGNS
          + ACCENTS
      )
      greek_string = "".join(
          [
              lem
              for lem in input_str
              if lem in greek_alphabet or lem == " "
          ]
      )
      #
      return greek_string.strip()
  
imports: from cltk.alphabet.text_normalization import cltk_normalize, remove_odd_punct, split_leading_punct, split_trailing_punct
label_desc: Use image node_id 2 for calling a global function with example usage: filter_non_greek(input_str) and returns: greek_string