def as_proj4(self):
        """
        Return the PROJ.4 string which corresponds to the CRS.

        For example::

            >>> print(get(21781).as_proj4())
            +proj=somerc +lat_0=46.95240555555556 +lon_0=7.439583333333333 \
+k_0=1 +x_0=600000 +y_0=200000 +ellps=bessel \
+towgs84=674.4,15.1,405.3,0,0,0,0 +units=m +no_defs

        """
        url = '{prefix}{code}.proj4?download'.format(prefix=EPSG_IO_URL,
                                                     code=self.id)
        return requests.get(url).text.strip()
Return the PROJ.4 string which corresponds to the CRS.

        For example::

            >>> print(get(21781).as_proj4())
            +proj=somerc +lat_0=46.95240555555556 +lon_0=7.439583333333333 \
+k_0=1 +x_0=600000 +y_0=200000 +ellps=bessel \
+towgs84=674.4,15.1,405.3,0,0,0,0 +units=m +no_defs