code: def _parse_request(self, schema, req, locations):
          
          if schema.many:
              assert (
                  "json" in locations
              ), "schema.many=True is only supported for JSON location"
              # The ad hoc Nested field is more like a workaround or a helper,
              # and it servers its purpose fine. However, if somebody has a desire
              # to re-design the support of bulk-type arguments, go ahead.
              parsed = self.parse_arg(
                  name="json",
                  field=ma.fields.Nested(schema, many=True),
                  req=req,
                  locations=locations,
              )
              if parsed is missing:
                  parsed = []
          else:
              argdict = schema.fields
              parsed = {}
              for argname, field_obj in iteritems(argdict):
                  if MARSHMALLOW_VERSION_INFO[0] < 3:
                      parsed_value = self.parse_arg(argname, field_obj, req, locations)
                      # If load_from is specified on the field, try to parse from that key
                      if parsed_value is missing and field_obj.load_from:
                          parsed_value = self.parse_arg(
                              field_obj.load_from, field_obj, req, locations
                          )
                          argname = field_obj.load_from
                  else:
                      argname = field_obj.data_key or argname
                      parsed_value = self.parse_arg(argname, field_obj, req, locations)
                  if parsed_value is not missing:
                      parsed[argname] = parsed_value
          return parsed
docs: Return a parsed arguments dictionary for the current request.