class_docstr: Helper object that allows to configure `characters` strategy with
  various unicode categories and characters. Also allows negation of
  configured set.
  
  :param negate: If True, configure :func:`hypothesis.strategies.characters`
      to match anything other than configured character set
  :param flags: Regex flags. They affect how and which characters are matched
class_docstr_tok: ["Helper","object","that","allows","to","configure","`","characters","`","strategy","with","various","unicode","categories","and","characters",".","Also","allows","negation","of","configured","set",".",":","param","negate",":","If","True",",","configure",":","func",":","`","hypothesis.strategies.characters","`","to","match","anything","other","than","configured","character","set",":","param","flags",":","Regex","flags",".","They","affect","how","and","which","characters","are","matched"]
docstr: Add given char to the whitelist.
docstr_tok: ["Add","given","char","to","the","whitelist","."]
code: def add_char(self, char, *, check=True):
      """Add given char to the whitelist."""
      c = self.code_to_char(char)
      if check and chars_not_in_alphabet(self._alphabet, c):
          raise InvalidArgument(
              f"Literal {c!r} is not in the specified alphabet"
          )
      self._whitelist_chars.add(c)
      if (
          self._ignorecase
          and re.match(re.escape(c), c.swapcase(), flags=re.IGNORECASE)
          is not None
      ):
          # Note that it is possible that `len(c.swapcase()) > 1`
          self._whitelist_chars.add(c.swapcase())
  
imports: import operator
  import re
  from hypothesis.errors import InvalidArgument
  from hypothesis.internal import charmap
  from hypothesis.strategies._internal.lazy import unwrap_strategies
  from hypothesis.strategies._internal.strings import OneCharStringStrategy
  from hypothesis import reject, strategies
  from hypothesis.internal.charmap import as_general_categories, categories
  from hypothesis.internal.compat import add_note, int_to_byte
label_desc: Use image node_id 4 for calling the CharactersBuilder obj's underlying member method code with example usage: obj.add_char(char) without return types