#define BSON_APPEND_DOCUMENT_BEGIN(b, key, child) \

       MongoDB, Inc

       2009-present, MongoDB, Inc.

1.30.4                                            Jun 08, 2025                     BSON_APPEND_DOCUMENT_BEGIN(3)

       The  bson_append_document_begin() function shall begin appending a sub-document to bson. Use child to add
       fields to the sub-document. When completed, call bson_append_document_end() to complete the element.

       childMUST be an uninitialized bson_t to avoid leaking memory.

       • bson: A bson_t.

       • key: An ASCII C string containing the name of the field.

       • key_length: The length of key in bytes, or -1 to determine the length with strlen().

       • child: An uninitialized bson_t to be initialized as the sub-document.

       Returns true if the operation was applied successfully. The function will fail if bson must  grow  larger
       than INT32_MAX.

          #define BSON_APPEND_DOCUMENT_BEGIN(b, key, child) \
             bson_append_document_begin (b, key, (int) strlen (key), child)

          bool
          bson_append_document_begin (bson_t *bson,
                                      const char *key,
                                      int key_length,
                                      bson_t *child);