Extract the value of the key defined in the map

Parameters:

- payload: Map. Container of the information (<key, value>) that is required.

- tag: String. Key to search within the map.

- list: List of String. List of tags to search in depth, by structure chaining.

- default_value: t(). Default value, in case it cannot be found. If not defined, it takes value nil.

Return:

- t() | nil. If the defined labels are correct, it returns the desired value; otherwise nil.

Extract the information and attach it to the defined map. If it does not appear, it gives the default value in each case.

###Parameters:

- payload_: Map. Payload.

- attr_list. List of InfoAttr. Fields to search for in the payload.

- eliminate_null_value: Boolean. Indicates if you want to eliminate fields with null values.

Return:

- list of {attr.id, values_extracted_from_the_payload} | empty list

Group the maps with equal value in a certain field

Parameters:

- list: List of map. Data.

- fields: Set of fields to set the identifier of each set. The identifier is the concatenation of each one, and the character '_'.

Return:

- {A, B} where

    A Map where values is a list of values of `list` such that they share the same value in the defined field

    B List of t() coincides with A.key()