docstr: Given a string containing a nominal type, returns a tuple of the
  possible values.
  
  A nominal type is defined as something framed between braces ({}).
  
  Parameters
  ----------
  atrv : str
     Nominal type definition
  
  Returns
  -------
  poss_vals : tuple
     possible values
  
  Examples
  --------
  >>> get_nom_val("{floup, bouga, fl, ratata}")
  ('floup', 'bouga', 'fl', 'ratata')
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code: def _get_nom_val(atrv):
      """Given a string containing a nominal type, returns a tuple of the
      possible values.
  
      A nominal type is defined as something framed between braces ({}).
  
      Parameters
      ----------
      atrv : str
         Nominal type definition
  
      Returns
      -------
      poss_vals : tuple
         possible values
  
      Examples
      --------
      >>> get_nom_val("{floup, bouga, fl, ratata}")
      ('floup', 'bouga', 'fl', 'ratata')
      """
      m = r_nominal.match(atrv)
      if m:
          attrs, _ = split_data_line(m.group(1))
          return tuple(attrs)
      else:
          raise ValueError("This does not look like a nominal string")
  
imports: import re
  import datetime
  import numpy
  import csv
  import ctypes
label_desc: Use image node_id 2 for calling the NominalAttribute obj's underlying member method code with example usage: obj._get_nom_val(atrv) and returns: tuple