code: def nameprep(label):
      # Map
      newlabel = []
      for c in label:
          if stringprep.in_table_b1(c):
              # Map to nothing
              continue
          newlabel.append(stringprep.map_table_b2(c))
      label = "".join(newlabel)
  
      # Normalize
      label = unicodedata.normalize("NFKC", label)
  
      # Prohibit
      for c in label:
          if (
              stringprep.in_table_c12(c)
              or stringprep.in_table_c22(c)
              or stringprep.in_table_c3(c)
              or stringprep.in_table_c4(c)
              or stringprep.in_table_c5(c)
              or stringprep.in_table_c6(c)
              or stringprep.in_table_c7(c)
              or stringprep.in_table_c8(c)
              or stringprep.in_table_c9(c)
          ):
              raise UnicodeError("Invalid character %r" % c)
  
      # Check bidi
      RandAL = map(stringprep.in_table_d1, label)
      for c in RandAL:
          if c:
              # There is a RandAL char in the string. Must perform further
              # tests:
              # 1) The characters in section 5.8 MUST be prohibited.
              # This is table C.8, which was already checked
              # 2) If a string contains any RandALCat character, the string
              # MUST NOT contain any LCat character.
              if filter(stringprep.in_table_d2, label):
                  raise UnicodeError("Violation of BIDI requirement 2")
  
              # 3) If a string contains any RandALCat character, a
              # RandALCat character MUST be the first character of the
              # string, and a RandALCat character MUST be the last
              # character of the string.
              if not RandAL[0] or not RandAL[-1]:
                  raise UnicodeError("Violation of BIDI requirement 3")
  
      return label
  
imports: import stringprep, re, codecs
  from unicodedata import ucd_3_2_0
label_desc: Use image node_id 1 for calling a global function with example usage: nameprep(label) and returns: label