Modifies a field to the embed object.

        The index must point to a valid pre-existing field.

        This function returns the class instance to allow for fluent-style
        chaining.

        Parameters
        -----------
        index: :class:`int`
            The index of the field to modify.
        name: :class:`str`
            The name of the field.
        value: :class:`str`
            The value of the field.
        inline: :class:`bool`
            Whether the field should be displayed inline.

        Raises
        -------
        IndexError
            An invalid index was provided.

def set_field_at(self, index, *, name, value, inline=True):
        """Modifies a field to the embed object.

        The index must point to a valid pre-existing field.

        This function returns the class instance to allow for fluent-style
        chaining.

        Parameters
        -----------
        index: :class:`int`
            The index of the field to modify.
        name: :class:`str`
            The name of the field.
        value: :class:`str`
            The value of the field.
        inline: :class:`bool`
            Whether the field should be displayed inline.

        Raises
        -------
        IndexError
            An invalid index was provided.
        """

        try:
            field = self._fields[index]
        except (TypeError, IndexError, AttributeError):
            raise IndexError('field index out of range')

        field['name'] = str(name)
        field['value'] = str(value)
        field['inline'] = inline
        return self