def string(self):
        r"""This is valid if and only if

        1. the expression is a :class:`.TexCmd` AND
        2. the command has only one argument.

        :rtype: Union[None,str]

        >>> from TexSoup import TexSoup
        >>> soup = TexSoup(r'''\textbf{Hello}''')
        >>> soup.textbf.string
        'Hello'
        >>> soup.textbf.string = 'Hello World'
        >>> soup.textbf.string
        'Hello World'
        >>> soup.textbf
        \textbf{Hello World}
        """
        if isinstance(self.expr, TexCmd) and len(self.expr.args) == 1:
            return self.expr.args[0].value
def string ( self ) : if isinstance ( self . expr , TexCmd ) and len ( self . expr . args ) == 1 : return self . expr . args [ 0 ] . value
r"""This is valid if and only if

        1. the expression is a :class:`.TexCmd` AND
        2. the command has only one argument.

        :rtype: Union[None,str]

        >>> from TexSoup import TexSoup
        >>> soup = TexSoup(r'''\textbf{Hello}''')
        >>> soup.textbf.string
        'Hello'
        >>> soup.textbf.string = 'Hello World'
        >>> soup.textbf.string
        'Hello World'
        >>> soup.textbf
        \textbf{Hello World}