code: def validate(self):
          
          # Get the first letter, or empty string if it doesn't exist.
          if not self.variable_name.startswith(u'$'):
              raise GraphQLCompilationError(u'Expected variable name to start with $, but was: '
                                            u'{}'.format(self.variable_name))
  
          if self.variable_name in RESERVED_MATCH_KEYWORDS:
              raise GraphQLCompilationError(u'Cannot use reserved MATCH keyword {} as variable '
                                            u'name!'.format(self.variable_name))
  
          validate_safe_string(self.variable_name[1:])
  
          if not is_graphql_type(self.inferred_type):
              raise ValueError(u'Invalid value of "inferred_type": {}'.format(self.inferred_type))
  
          if isinstance(self.inferred_type, GraphQLNonNull):
              raise ValueError(u'GraphQL non-null types are not supported as "inferred_type": '
                               u'{}'.format(self.inferred_type))
  
          if isinstance(self.inferred_type, GraphQLList):
              inner_type = strip_non_null_from_type(self.inferred_type.of_type)
              if GraphQLDate.is_same_type(inner_type) or GraphQLDateTime.is_same_type(inner_type):
                  # This is a compilation error rather than a ValueError as
                  # it can be caused by an invalid GraphQL query on an otherwise valid schema.
                  # In other words, it's an error in writing the GraphQL query, rather than
                  # a programming error within the library.
                  raise GraphQLCompilationError(
                      u'Lists of Date or DateTime cannot currently be represented as '
                      u'Variable objects: {}'.format(self.inferred_type))
docs: Validate that the Variable is correctly representable.