'Look for rdata with the specified name and type in the zone,
and return an RRset encapsulating it.
The I{name}, I{rdtype}, and I{covers} parameters may be
strings, in which case they will be converted to their proper
type.
This method is less efficient than the similar L{get_rdataset}
because it creates an RRset instead of returning the matching
rdataset.  It may be more convenient for some uses since it
returns an object which binds the owner name to the rdata.
This method may not be used to create new nodes or rdatasets;
use L{find_rdataset} instead.
None is returned if the name or type are not found.
Use L{find_rrset} if you want to have KeyError raised instead.
@param name: the owner name to look for
@type name: DNS.name.Name object or string
@param rdtype: the rdata type desired
@type rdtype: int or string
@param covers: the covered type (defaults to None)
@type covers: int or string
@rtype: dns.rrset.RRset object'

def get_rrset(self, name, rdtype, covers=dns.rdatatype.NONE):

    try:
        rrset = self.find_rrset(name, rdtype, covers)
    except KeyError:
        rrset = None
    return rrset
