Rest API source is not callable

[willi-mueller]

Source name
Generic REST API #313

Make sure that

• I checked the README in the source folder
• If I have problems with the credentials I checked the credentials docs and troubleshooting

Describe the bug

The resource returned by rest_api.rest_api_source() is not callable

To Reproduce

@dlt.resource(name='table_name', write_disposition='replace')
def generate_rows():
    for i in range(10):
        yield {'id':i, 'example_string':'abc'}

@dlt.source
def source_name():
    return generate_rows


pokemon_source = rest_api_source({
    "client": {
        "base_url": "https://pokeapi.co/api/v2/",
        "default_paginator": "json_links",
    },
    "endpoints": {
        "pokemon": {
            "params": {
                "limit": 100, # Default page size is 20
            },
            "resource": {
                "primary_key": "id",
            }
        },
    },
})

print(list(source_name().with_resources('table_name').add_limit(1)))  # works
print(list(pokemon_source.with_resources('pokemon').add_limit(1)))  # returns 1 page of data
print(list(pokemon_source.pokemon.add_limit(1)))  # returns 1 page of data
print(list(pokemon_source().with_resources('pokemon').add_limit(1))) # crashes: TypeError: 'DltSource' object is not callable

Expected behavior

I'm not sure if it should return one page or data or 1 record. Since it calls the paginator I think 1 page is fine.

print(list(pokemon_source().with_resources('pokemon').add_limit(1))) # should it return only 1 record instead of 1 page?

print(list(pokemon_source().with_resources('pokemon').add_limit(1))) # should not crash?

Running environment

• OS: MacOs
• dlt Version 0.4.4
• verified-sources 4428038

Additional context
I tried to implement a function that checks if the source can connect to the API endpoint by fetching only the first page of a resource.