class_docstr: Object to validate a list of strings to use as field names.
  
  The strings are stripped of any non alphanumeric character, and spaces
  are replaced by '_'. During instantiation, the user can define a list
  of names to exclude, as well as a list of invalid characters. Names in
  the exclusion list are appended a '_' character.
  
  Once an instance has been created, it can be called with a list of
  names, and a list of valid names will be created.  The `__call__`
  method accepts an optional keyword "default" that sets the default name
  in case of ambiguity. By default this is 'f', so that names will
  default to `f0`, `f1`, etc.
  
  Parameters
  ----------
  excludelist : sequence, optional
      A list of names to exclude. This list is appended to the default
      list ['return', 'file', 'print']. Excluded names are appended an
      underscore: for example, `file` becomes `file_` if supplied.
  deletechars : str, optional
      A string combining invalid characters that must be deleted from the
      names.
  case_sensitive : {True, False, 'upper', 'lower'}, optional
      * If True, field names are case-sensitive.
      * If False or 'upper', field names are converted to upper case.
      * If 'lower', field names are converted to lower case.
  
      The default value is True.
  replace_space : '_', optional
      Character(s) used in replacement of white spaces.
  
  Notes
  -----
  Calling an instance of `NameValidator` is the same as calling its
  method `validate`.
  
  Examples
  --------
  >>> validator = np.lib._iotools.NameValidator()
  >>> validator(['file', 'field2', 'with space', 'CaSe'])
  ('file_', 'field2', 'with_space', 'CaSe')
  
  >>> validator = np.lib._iotools.NameValidator(excludelist=['excl'],
  ...                                           deletechars='q',
  ...                                           case_sensitive=False)
  >>> validator(['excl', 'field2', 'no_q', 'with space', 'CaSe'])
  ('EXCL', 'FIELD2', 'NO_Q', 'WITH_SPACE', 'CASE')
code: def __call__(self, names, defaultfmt="f%i", nbfields=None):
      return self.validate(
          names, defaultfmt=defaultfmt, nbfields=nbfields
      )
  
imports: import numpy
  import numpy._core.numeric
  from numpy._utils import asbytes, asunicode
label_desc: Use image node_id 3 for calling the NameValidator obj's underlying member method code with example usage: obj.__call__(names, defaultfmt, nbfields) and returns: self