.Str: ClassType
.Str.
'''
Return a capitalized version of the string.
More specifically, make the first character have upper case and the rest lower
case.
'''
'''erg
assert "hello".capitalize() == "Hello"
assert "HELLO".capitalize() == "Hello"
'''
capitalize: (self: .Str) -> .Str
'''
Return a version of the string suitable for caseless comparisons.
'''
'''erg
assert "camelCase".casefold() == "camelcase"
assert "CamelCase".casefold() == "camelcase"
assert "FULLCAPS".casefold() == "fullcaps"
assert "snake_case".casefold() == "snake_case"
'''
casefold: (self: .Str) -> .Str
'''
Return a centered string of length width.
Padding is done using the specified fill character (default is a space).
'''
'''erg
assert "hello".center(10) == " hello "
assert "hello".center(10, "-") == "--hello---"
'''
center: (self: .Str, width: Int, fillchar := .Str) -> .Str