'Return a field instance given the name of a forward or reverse field.'

def get_field(self, field_name):

    try:
        return self._forward_fields_map[field_name]
    except KeyError:
        if (not self.apps.models_ready):
            raise FieldDoesNotExist(("%s    has    no    field    named    '%s'.    The    app    cache    isn't    ready    yet,    so    if    this    is    an    auto-created    related    field,    it    won't    be    available    yet." % (self.object_name, field_name)))
    try:
        return self.fields_map[field_name]
    except KeyError:
        raise FieldDoesNotExist(("%s    has    no    field    named    '%s'" % (self.object_name, field_name)))
