code: def pretty_atom(atom_name, default=None, printer=None):
      """return pretty representation of an atom"""
      if _use_unicode:
          if (
              printer is not None
              and atom_name == "ImaginaryUnit"
              and printer._settings["imaginary_unit"] == "j"
          ):
              return U("DOUBLE-STRUCK ITALIC SMALL J")
          else:
              return atoms_table[atom_name]
      else:
          if default is not None:
              return default
  
          raise KeyError("only unicode")
  
imports: import sys
  import warnings
  from string import ascii_lowercase, ascii_uppercase
  import unicodedata
  from sympy.printing.conventions import split_super_sub
  from sympy.core.alphabets import greeks
  from sympy.utilities.exceptions import sympy_deprecation_warning
label_desc: Use image node_id 9 for calling a global function with example usage: pretty_atom(atom_name, default, printer) and returns: U, atoms_table, default