I am writing a PyQGIS script (Python version 3.9) within FME Workbench 2024.1.2 Python caller transformer which has to run some processing tasks from the QGIS (LTR 3.34.4) processing framework:

import fme
import fmeobjects
import sys

from qgis.core import QgsApplication, QgsVectorLayer, QgsProcessingFeedback

class FeatureProcessor(object):
    """Template Class Interface:
    When using this class, make sure its name is set as the value of the 'Class to Process Features'
    transformer parameter.
    """

    def __init__(self):
        """Base constructor for class members."""
        # Initialize QGIS Application
        QgsApplication.setPrefixPath("F:/QGIS 3.34.4/apps/qgis-ltr", True)
        self.qgs = QgsApplication([], False)
        self.qgs.initQgis()

        # Append the path where processing plugin can be found
        sys.path.append('F:/QGIS 3.34.4/apps/qgis-ltr/python/plugins/processing')

        from processing.core.Processing import Processing
        Processing.initialize()
        import processing

    def has_support_for(self, support_type: int):
        """This method is called by FME to determine if the PythonCaller supports Bulk mode,
        which allows for significant performance gains when processing large numbers of features.
        Bulk mode cannot always be supported. 
        More information available in transformer help.
        """
        return support_type == fmeobjects.FME_SUPPORT_FEATURE_TABLE_SHIM

    def input(self, feature: fmeobjects.FMEFeature):
        """This method is called for each feature which enters the PythonCaller. 
        Processed input features can be emitted from this method using self.pyoutput().
        If knowledge of all input features is required for processing, then input features should be 
        cached to a list instance variable and processed using group processing or in the close() method.
        """
        gpkg_path = feature.getAttribute("path_windows")
        layer_name = feature.getAttribute("path_filename")

        # Open the specified layer in the GeoPackage
        layer = QgsVectorLayer(gpkg_path, layer_name + '|layername=' + layer_name, 'ogr')
        crs = layer.crs().authid()
        feature.setAttribute("CRS", crs)


        params = {'INPUT': layer,
        'ALL_PARTS': False,
        'OUTPUT': 'memory:'}
        result = processing.run("native:centroids", params)
        centroid_layer = result['OUTPUT']

        self.pyoutput(feature)

    def close(self):
        """This method is called once all the FME Features have been processed from input()."""
        self.qgs.exitQgis()

    def process_group(self):
        """This method is called by FME for each group when group processing mode is enabled.
        This implementation should reset any instance variables used for the next group. 
        Bulk mode should not be enabled when using group processing. 
        More information available in transformer help.
        """
        pass

The QGIS core functionalities ran successfully (crs attribute with EPSG:4326 was added to the attribute table), so the python env settings should be correct. But processing framework seems not to be recognized. 

Errors according to log file:

ERROR	Message Type: fme::internal::_v0::Exception
ERROR	Python Exception <NameError>: name 'processing' is not defined
ERROR	Error encountered while calling method `input'
FATAL	PythonCaller (PythonFactory): PythonFactory failed to process feature

Preferred Python interpreter (FME Options → Translation) is set to the Python39 dll file:

F:\QGIS 3.34.4\apps\Python39\python39.dll

Python Home (PYTHONHOME): F:\QGIS 3.34.4\apps\Python39

Environment variables for system user are:

PYTHON: F:\Apps\FMEForm\2024_1_2\python

PYTHONHOME: F:\QGIS 3.34.4\bin

PYTHONPATH: F:\QGIS 3.34.4\apps\qgis-ltr\python; F:\QGIS 3.34.4\apps\qgis-ltr\python\plugins

(Python Compatibility in Workspace set to Python 3.9+)

By only importing the processing module no error occurs. By running a processing algorithm, the above errors appear so no processing algorithm can be run.

Can you please help with this? Thank you!