fix: correct return value for coincidence_collect

coincidence_collect can now return "None" when there are no coincidences

build: build system can now detect if running locally or on CI

setup.py

@@ -4,13 +4,7 @@
 from Cython.Build import cythonize
 from setuptools import setup, Extension
 
-
-local = True
-print("CIBUILDWHEEL ", os.environ.get("CIBUILDWHEEL", '0'))
-if os.environ.get("CIBUILDWHEEL", '0') == 1:
-    local = False
-local = False
-
+local = os.path.isdir("./local_testing/")
 cython_dir = os.path.join("tangy_src")
 
 extensions = []

tangy_src/_tangy.py

@@ -1,5 +1,6 @@
 import cython
 from cython.cimports import _tangy as _tangy
+import warnings
 
 import mmap
 from os import dup, listdir, remove, makedirs
@@ -974,7 +975,7 @@ def coincidence_count(self, read_time: float, window: float,
     @cython.ccall
     def coincidence_collect(self, read_time: float, window: float,
                             channels: List[int],
-                            delays: Optional[List[float]] = None) -> Records:
+                            delays: Optional[List[float]] = None) -> Optional[Records]:
         """ Collect coincident timetags
 
         Collects the timetags in coincdience for the chosen channels over the
@@ -1021,6 +1022,10 @@ def coincidence_collect(self, read_time: float, window: float,
                                                  read_time,
                                                  cython.address(self._buf.records))
 
+        if count == 0:
+            warnings.warn("No coincidences found")
+            return None
+
         slice: _tangy.tangy_field_ptrs
         n_records: u64n = count * _n_channels
 
@@ -1731,7 +1736,7 @@ def __init__(self, file_path: str, name: str, length: int = 1000):
             name, 1e-12, 1, 8, length, TangyBufferType.Standard)
 
         self._timetag_offset = _tangy.srb_read_header_qutools(
-                self._buffer._ptr_rb, self._c_file_handle)
+            self._buffer._ptr_rb, self._c_file_handle)
         return
 
     def __del__(self):