code: def solidity_library_symbol(library_name):
      
      # the symbol is always 40 characters in length with the minimum of two
      # leading and trailing underscores
      length = min(len(library_name), 36)
  
      library_piece = library_name[:length]
      hold_piece = '_' * (36 - length)
  
      return '__{library}{hold}__'.format(
          library=library_piece,
          hold=hold_piece,
      )
docs: Return the symbol used in the bytecode to represent the `library_name`.