code: def convert(self, value, param, ctx):
      try:
          rex = re.compile(value, re.IGNORECASE)
      except ValueError:
          self.fail(
              "%s is not a valid regular expression." % value,
              param,
              ctx,
          )
      else:
          return rex
  
file_path: nipype/nipype/scripts/utils.py
imports: import re
  import click
  import json
  from .instance import import_module
  from ..interfaces.base import InputMultiPath, traits
  from ..interfaces.base.support import get_trait_desc
label_desc: Use image node_id 1 for calling the RegularExpression obj's underlying member method code with example usage: obj.convert(value, param, ctx) and returns: rex