Price as midpoint between bid and ask.

        Parameters
        ----------
        opttype : str
            'call' or 'put'.
        strike : numeric
            Strike price.
        expiry : date-like
            Expiration date. Can be a :class:`datetime.datetime` or
            a string that :mod:`pandas` can interpret as such, e.g.
            '2015-01-01'.

        Returns
        -------
        out : float

        Examples
        --------
        >>> geopts = pn.opt.get('ge')
        >>> geopts.price.get('call', 26., '2015-09-18')
        0.94

def get(self, opttype, strike, expiry):
        """
        Price as midpoint between bid and ask.

        Parameters
        ----------
        opttype : str
            'call' or 'put'.
        strike : numeric
            Strike price.
        expiry : date-like
            Expiration date. Can be a :class:`datetime.datetime` or
            a string that :mod:`pandas` can interpret as such, e.g.
            '2015-01-01'.

        Returns
        -------
        out : float

        Examples
        --------
        >>> geopts = pn.opt.get('ge')
        >>> geopts.price.get('call', 26., '2015-09-18')
        0.94
        """
        _optrow = _relevant_rows(self.data, (strike, expiry, opttype,),
                "No key for {} strike {} {}".format(expiry, strike, opttype))
        return _getprice(_optrow)